Gre阅读真题200篇 brief contents

səhifə	11/99
tarix	25.06.2016
ölçüsü	3.1 Mb.

1 ... 7 8 9 10 11 12 13 14 ... 99

Until about five years ago,

Until about five years ago, the very idea that peptide (peptide: n.缩氨酸) hormones might be made anywhere in the brain besides the hypothalamus was astounding. Peptide hormones, scientists thought, were made by endocrine glands and the hypothalamus was thought to be the brains’ only endocrine gland. What is more, because peptide hormones cannot cross the blood-brain barrier, researchers believed that they never got to any part of the brain other than the hypothalamus, where they were simply produced and then released into the bloodstream.

But these beliefs about peptide hormones were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present. The immunological method of detecting peptide hormones by means of antiserums, however, is imprecise. Cross-reactions are possible and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives. Furthermore, this method cannot be used to determine the location in the body where the detected substances are actually produced.

New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNA’s (cDNA’s) that can serve as molecular probes to seek out the messenger RNA’s (mRNA’s) of the peptide hormones. If brain cells are making the hormones, the cells will contain these mRNA’s. If the products the brain cells make resemble the hormones but are not identical to them, then the cDNA’s should still bind to these mRNA’s, but should not bind as tightly as they would to mRNA’s for the true hormones. The cells containing these mRNA’s can then be isolated and their mRNA’s decoded to determine just what their protein products are and how closely the products resemble the true peptide hormones.

The molecular approach to detecting peptide hormones using cDNA probes should also be much faster than the immunological method because it can take years of tedious purifications to isolate peptide hormones and then develop antiserums to them. Roberts, expressing the sentiment of many researchers, states: “I was trained as an endocrinologist. But it became clear to me that the field of endocrinology needed molecular biology input. The process of grinding out protein purifications is just too slow.”

If, as the initial tests with cDNA probes suggest, peptide hormones really are made in the brain in areas other than the hypothalamus, a theory must be developed that explains their function in the brain. Some have suggested that the hormones are all growth regulators, but Rosen’s work on rat brains indicates that this cannot be true. A number of other researchers propose that they might be used for intercellular communication in the brain.

21. Which of the following titles best summarizes the passage?

(A) Is Molecular Biology the Key to Understanding Intercellular Communication in the Brain?

(B) Molecular Biology: Can Researchers Exploit Its Techniques to Synthesize Peptide Hormones?

(D) Peptide Hormones: How Scientists Are Attempting to Solve Problems of Their Detection and to Understand Their Function（D）

(E) Peptide Hormones: The Role Played by Messenger RNA’s in Their Detection

22. The passage suggests that a substance detected in the brain by use of antiserums to peptide hormones may

(A) have been stored in the brain for a long period of time

(B) play no role in the functioning of the brain

(D) have escaped detection by molecular methods（C）

(E) play an important role in the functioning of the hypothalamus

23. According to the passage, confirmation of the belief that peptide hormones are made in the brain in areas other than the hypothalamus would force scientists to

(A) reject the theory that peptide hormones are made by endocrine glands

(B) revise their beliefs about the ability of antiserums to detect peptide hormones

(D) search for techniques that would enable them to distinguish peptide hormones from their close relatives（E）

(E) develop a theory that explains the role played by peptide hormones in the brain

24. Which of the following is mentioned in the passage as a drawback of the immunological method of detecting peptide hormones?（C张冠李戴，但颇具迷惑性）

(A) It cannot be used to detect the presence of growth regulators in the brain.

(B) It cannot distinguish between the peptide hormones and substances that are very similar to them.

(D) It involves a purification process that requires extensive training in endocrinology.（B）

(E) It involves injecting foreign substances directly into the bloodstream.

25. The passage implies that, in doing research on rat brains, Rosen discovered that

(A) peptide hormones are used for intercellular communication

(B) complementary DNA’s do not bind to cells producing peptide hormones

(D) some peptide hormones do not function as growth regulators（D）

(E) antiserums cross-react with substances that are not peptide hormones

26. Which of the following is a way in which the immunological method of detecting peptide hormones differs from the molecular method?

(A) The immunological method uses substances that react with products of hormone-producing cells, whereas the molecular method uses substances that react with a specific component of the cells themselves.

(B) The immunological method has produced results consistent with long-held beliefs about peptide hormones, whereas the molecular method has produced results that upset these beliefs.

(C) The immunological method requires a great deal of expertise, whereas the molecular method has been used successfully by nonspecialists.

(D) The immunological method can only be used to test for the presence of peptide hormones within the hypothalamus, whereas the molecular method can be used throughout the brain.（A）

(E) The immunological method uses probes that can only bind with peptide hormones, whereas the molecular method uses probes that bind with peptide hormones and substances similar to them.

27. The idea that the field of endocrinology can gain from developments in molecular biology is regarded by Roberts with

(A) incredulity

(B) derision

(D) pride（E）

(E) enthusiasm

Echolocating bats emit sounds

Echolocating bats emit sounds in patterns—characteristic of each species—that contain both frequency-modulated (FM) and constant-frequency (CF) signals. The broadband FM signals and the narrowband CF signals travel out to a target, reflect from it, and return to the hunting bat. In this process of transmission and reflection, the sounds are changed, and the changes in the echoes enable the bat to perceive features of the target.

The FM signals report information about target characteristics that modify the timing and the fine frequency structure, or spectrum, of echoes—for example, the target’s size, shape, texture, surface structure, and direction in space. Because of their narrow bandwidth, CF signals portray only the target’s presence and, in the case of some bat species, its motion relative to the bat’s. Responding to changes in the CF echo’s frequency, bats of some species correct in flight for the direction and velocity of their moving prey.

24. According to the passage, the information provided to the bat by CF echoes differs from that provided by FM echoes in which of the following ways?

(A) Only CF echoes alert the bat to moving targets.

(B) Only CF echoes identify the range of widely spaced targets.

(D) In some species, CF echoes enable the bat to judge whether it is closing in on its target.（D）

(E) In some species, CF echoes enable the bat to discriminate the size of its target and the direction in which the target is moving.

25. According to the passage, the configuration of the target is reported to the echolocating bat by changes in the

(A) echo spectrum of CF signals

(B) echo spectrum of FM signals

(D) delay between transmission and reflection of the CF signals（B）

(E) relative frequencies of the FM and the CF echoes

26. The author presents the information concerning bat sonar in a manner that could be best described as

(A) argumentative

(B) commendatory

(D) disbelieving（E）

(E) objective

27. Which of the following best describes the organization of the passage?

(A) A fact is stated, a process is outlined, and specific details of the process are described.

(B) A fact is stated, and examples suggesting that a distinction needs correction are considered.

(C) A fact is stated, a theory is presented to explain that fact, and additional facts are introduced to validate the theory.

(D) A fact is stated, and two theories are compared in light of their explanations of this fact.（A）

(E) A fact is stated, a process is described, and examples of still another process are illustrated in detail.

Typically the queen honeybee

Typically the queen honeybee is mother to all the bees in a hive; after mating with several male drones from other colonies, she lays fertilized eggs that develop into all-female worker bees and lays unfertilized eggs that become all-male drones. When a queen dies, workers often lay unfertilized eggs that hatch into drones. Yet workers rarely reproduce while a queen reigns.

According to natural selection (natural selection: n.[生]自然选择,物竞天择说) theory, a worker would enhance her fitness—or ability to propagate her genes—by hatching her own eggs in addition to or in place of the queen’s. But a typical worker’s fitness would be diminished if other workers’ sons, who have less genetic material in common with the worker, supplanted the queen’s sons (the worker’s brothers). Researchers, testing the hypothesis that workers usually somehow block each other’s attempts to reproduce, put unfertilized eggs laid by workers and by the queen into a hive. Other workers quickly devoured the workers’ eggs while leaving the queen’s eggs alone.

17. The author refers to the experiment described in lines 16-19 in order to

(A) explain how worker bees are prevented from mating with drones

(B) explain how worker bees hatch and nurture the queen’s young

(D) show that worker bees are capable of thwarting each other’s attempts to reproduce（D）

(E) provide a model of daily life in a typical honeybee hive

18. The inner workings in a honeybee hive that regulate reproduction, as they are described in the passage, are most similar to which of the following types of human societies?

(A) A totalitarian society in which citizens’ “policing” of each other’s actions helps to maintain the status quo.

(B) A pacifist state in which the individuals are strongly opposed to the use of violence or aggression to settle disputes.

(D) A parliamentary society in which a few members, organized as a cabinet wield executive power.（A）

(E) An anarchic state in which order and stable social structures are lacking.

19. The passage best supports which of the following inferences about the fitness of honeybees?

(A) Reproduction diminishes any individual honeybee’s fitness.

(B) An individual worker’s fitness can be maintained without the individual herself reproducing.

(C) A hierarchy of stronger and weaker individuals among the worker bees determines which individuals will reproduce when a queen dies.

(D) While a queen reigns, the fitness of the worker bees is increased and that of the drones is diminished.（B）

(E) Fitness encourages worker bees to hatch honeybee eggs without regard for the relatedness of the young to the “parent.”

20. The passage suggests which of the following about the eggs laid by worker bees?

(A) One of the eggs hatches into the next queen.

(B) The eggs are invariably destroyed by other worker bees.

(D) The eggs hatch only if the worker has mated with a drone from another hive.（E）

(E) The eggs are less likely to be harmed by other workers if the queen is dead.

While it is true that living organisms

While it is true that living organisms are profoundly affected by their environment, it is equally important to remember that many organisms are also capable of altering their habitat significantly, sometimes limiting their own growth. The influence of the biological component of an ecosystem is often greater in fresh waters than that in marine or terrestrial systems, because of the small size of many freshwater bodies. Many of the important effects of organisms are related to their physiology, especially growth and respiration. By their growth many species can deplete essential nutrients within the system, thus limiting their own growth or that of other species. Lund has demonstrated that in Lake Windermere the alga Asterionella is unable to grow in conditions that it itself has created. Once a year, in the spring, this plant starts to grow rapidly in the lake, using up so much silica from the water that by late spring there is no longer enough to maintain its own growth. The population decreases dramatically as a result.

24. Which of the following is an example of the type of organism described in the first sentence?

(A) A kind of ant that feeds on the sweet juice exuded by the twigs of a species of thorn tree that grows in dry areas.

(B) A kind of fish that, after growing to maturity in the ocean, returns to fresh water.

(C) A kind of flower that has markings distinctly perceptible in ultraviolet light to the species of bee that pollinates the flower.

(D) A kind of tree with seeds that germinate readily only in a sunny spot and then develop into mature trees that shade the area below them.（D）

(E) A kind of butterfly, itself nonpoisonous, with the same markings as a kind of butterfly that birds refuse to eat because it is poisonous.

25. It can be inferred from the passage that which of the followings is true about Asterionella plants in Lake Windermere?

(A) They are not present except in early spring.

(B) They contribute silica to the waters as they grow.

(D) They form a silica-rich layer on the lake bottom.（E）

(E) Their growth peaks in the spring.

26. The passage indicates that organisms frequently have the strongest effects on their environment in

(A) oceans, since oceans contain the largest organisms living on Earth

(B) oceans, since oceans provide habitats for many different kinds of species

(D) freshwater lakes, since nutrients in freshwater lakes are present only in small amounts（C）

(E) land areas, since there exist major influences of climate on the kinds of small organisms supported in land areas

27. The primary topic of the passage is the way in which

(A) organisms are affected by the amount of nutrients available

(B) organisms can change their own surroundings

(D) the reproduction of organisms is controlled by factors in the environment（B）

(E) plant matter in a given locale can increase up to a limit

As people age, their cells

As people age, their cells become less efficient and less able to replace damaged components. At the same time their tissues stiffen. For example, the lungs and the heart muscle expand less successfully, the blood vessels become increasingly rigid, and the ligaments and tendons tighten.

Few investigators would attribute such diverse effects to a single cause. Nevertheless, researchers have discovered that a process long known to discolor and toughen foods may also contribute to age-related impairment of both cells and tissues. That process is nonenzymatic glycosylation, whereby glucose becomes attached to proteins without the aid of enzymes. When enzymes attach glucose to proteins (enzymatic glycosylation), they do so at a specific site on a specific protein molecule for a specific purpose. In contrast, the nonenzymatic process adds glucose haphazardly to any of several sites along any available peptide chain within a protein molecule.

This nonenzymatic glycosylation of certain proteins has been understood by food chemists for decades, although few biologists recognized until recently that the same steps could take place in the body. Nonenzymatic glycosylation begins when an aldehyde group (CHO) of glucose and an amino group (NH2) of a protein are attracted to each other. The molecules combine, forming what is called a Schiff base within the protein. This combination is unstable and quickly rearranges itself into a stabler, but still reversible, substance known as an Amadori product.

If a given protein persists in the body for months or years, some of its Amadori products slowly dehydrate and rearrange themselves yet again, into new glucose-derived structures. These can combine with various kinds of molecules to form irreversible structures named advanced glycosylation end products (AGE’s). Most AGE’s are yellowish brown and fluorescent and have specific spectrographic properties. More important for the body, many are also able to cross-link adjacent proteins, particularly ones that give structure to tissues and organs. Although no one has yet satisfactorily described the origin of all such bridges between proteins, many investigators agree that extensive cross-linking of proteins probably contributes to the stiffening and loss of elasticity characteristic of aging tissues.

In an attempt to link this process with the development of cataracts (the browning and clouding of the lens of the eye as people age), researchers studied the effect of glucose on solutions of purified crystallin, the major protein in the lens of the eye. Glucose-free solutions remained clear, but solutions with glucose caused the proteins to form clusters, suggesting that the molecules had become cross-linked. The clusters diffracted light, making the solution opaque. The researchers also discovered that the pigmented cross-links in human cataracts have the brownish color and fluorescence characteristic of AGE’s. These data suggest that nonenzymatic glycosylation of lens crystallins may contribute to cataract formation.

17. With which of the following statements concerning the stiffening of aging tissues would the author most likely agree?

(A) It is caused to a large degree by an increased rate of cell multiplication.

(B) It paradoxically both helps and hinders the longevity of proteins in the human body.

(D) It is exacerbated by increased enzymatic glycosylation.（E）

(E) It probably involves the nonenzymatic glycosylation of proteins.

18. According to the passage, which of the following statements is true of the process that discolors and toughens foods?

(A) It takes place more slowly than glycosylation in the human body.

(B) It requires a higher ratio of glucose to protein than glycosylation requires in the human body.

(D) It proceeds more quickly when the food proteins have a molecular structure similar to that of crystallin proteins.（C）

(E) Its effectiveness depends heavily on the amount of environmental moisture.

19. According to the passage, which of the following is characteristic of enzymatic glycosylation of proteins?

(A) AGE’s are formed after a period of months or years.

(B) Proteins affected by the process are made unstable.

(D) Glucose is attached to proteins for specific purposes.（D）

(E) Amino groups combine with aldehyde groups to form Schiff bases.

20. According to the passage, which of the following statements is true of Amadori products in proteins?

(A) They are more plentiful in a dehydrated environment.

(B) They are created through enzymatic glycosylation.

(D) They are derived from Schiff bases.（D）

(E) They are derived from AGE’s.

21. Which of the following best describes the function of the third paragraph of the passage (lines 19-29)?

(A) It offers evidence that contradicts the findings described in the first two paragraphs.

(B) It presents a specific example of the process discussed in the first two paragraphs.

(D) It evaluates the research discoveries described in the previous paragraph.（E）

(E) It begins a detailed description of the process introduced in the previous two paragraphs.

22. The passage suggests that which of the following would be LEAST important in determining whether nonenzymatic glycosylation is likely to have taken place in the proteins of a particular tissue?

(A) The likelihood that the tissue has been exposed to free glucose

(B) The color and spectrographic properties of structures within the tissue

(D) The number of amino groups within the proteins in the tissue（D）

(E) The degree of elasticity that the tissue exhibits

23. If the hypothesis stated in lines 56-58 is true, it can be inferred that the crystallin proteins in the lenses of people with cataracts

(A) have increased elasticity

(B) do not respond to enzymatic glycosylation

(D) are at least several months old（D）

(E) respond more acutely than other proteins to changes in moisture levels

Hydrogeology is a science dealing

Hydrogeology is a science dealing with the properties, distribution, and circulation of water on the surface of the land, in the soil and underlying rocks, and in the atmosphere. The hydrologic cycle, a major topic in this science, is the complete cycle of phenomena through which water passes, beginning as atmospheric water vapor, passing into liquid and solid form as precipitation, thence along and into the ground surface, and finally again returning to the form of atmospheric water vapor by means of evaporation and transpiration.

The term “geohydrology” is sometimes erroneously used as a synonym for “hydrogeology.” Geohydrology is concerned with underground water. There are many formations that contain water but are not part of the hydrologic cycle because of geologic changes that have isolated them underground. These systems are properly termed geohydrologic but not hydrogeologic. Only when a system possesses natural or artificial boundaries that associate the water within it with the hydrologic cycle may the entire system properly be termed hydrogeologic.

17. The author’s primary purpose is most probably to

(A) present a hypothesis

(B) refute an argument

(D) predict an occurrence（C）

(E) describe an enigma

18. It can be inferred that which of the following is most likely to be the subject of study by a geohydrologist?

(A) Soft, porous rock being worn away by a waterfall

(B) Water depositing minerals on the banks of a gorge through which the water runs

(D) Water becoming unfit to drink through the release of pollutants into it from a manufacturing plant（C）

(E) The changing course of a river channel as the action of the water wears away the rocks past which the river flows

19. The author refers to “many formations” (line 16) primarily in order to

(A) clarify a distinction

(B) introduce a subject

(D) emphasize a similarity（A）

(E) resolve a conflict

Our visual perception depends on the

Our visual perception depends on the reception of energy reflecting or radiating from that which we wish to perceive. If our eyes could receive and measure infinitely delicate sense-data, we could perceive the world with infinite precision. The natural limits of our eyes have, of course, been extended by mechanical instruments; telescopes and microscopes, for example, expand our capabilities greatly. There is, however, an ultimate limit beyond which no instrument can take us; this limit is imposed by our inability to receive sense-data smaller than those conveyed by an individual quantum of energy. Since these quanta are believed to be indivisible packages of energy and so cannot be further refined, we reach a point beyond which further resolution of the world is not possible. It is like a drawing a child might make by sticking indivisible discs of color onto a canvas.

We might think that we could avoid this limitation by using quanta with extremely long wavelengths; such quanta would be sufficiently sensitive to convey extremely delicate sense-data. And these quanta would be useful, as long as we only wanted to measure energy, but a completely accurate perception of the world will depend also on the exact measurement of the lengths and positions of what we wish to perceive. For this, quanta of extremely long wavelengths are useless. To measure a length accurately to within a millionth of an inch, we must have a measure graduated in millionths of an inch; a yardstick graduated in inches in useless. Quanta with a wavelength of one inch would be, in a sense, measures that are graduated in inches. Quanta of extremely long wavelength are useless in measuring anything except extremely large dimensions.

Despite these difficulties, quanta have important theoretical implications for physics. It used to be supposed that, in the observation of nature, the universe could be divided into two distinct parts, a perceiving subject and a perceived object. In physics, subject and object were supposed to be entirely distinct, so that a description of any part of the universe would be independent of the observer. The quantum theory (quantum theory: 量子论), however, suggests otherwise, for every observation involves the passage of a complete quantum from the object to the subject, and it now appears that this passage constitutes an important coupling between observer and observed. We can no longer make a sharp division between the two in an effort to observe nature objectively. Such an attempt at objectivity would distort the crucial interrelatioship of observer and observed as parts of a single whole. But, even for scientists, it is only in the world of atoms that this new development makes any appreciable difference in the explanation of observations.

17. The primary purpose of the passage is to

(A) discuss a problem that hinders precise perception of the world

(B) point out the inadequacies of accepted units of measurement

(D) compare and contrast rival scientific hypotheses about how the world should be measured and observed（A）

(E) suggest the limited function of sensory observation

18. According to the passage, quanta with an extremely long wavelength cannot be used to give complete information about the physical world because they

(A) exist independently of sense-data

(B) are graduated only in inches

(D) cannot, with present-day instruments, be isolated from quanta of shorter wavelength（E）

(E) provide an insufficiently precise means of measuring length and position

19. Which of the following describes a situation most analogous to the situation discussed in lines 9-13?

(A) A mathematician can only solve problems the solution of which can be deduced from known axiom.

(B) An animal can respond to no command that is more complicated syntactically than any it has previously received.

(C) A viewer who has not learned, at least intuitively, the conventions of painting, cannot understand perspective in a drawing.

(D) A sensitized film will record no detail on a scale that is smaller than the grain of the film.（D）

(E) A shadow cast on a screen by an opaque object will have sharp edge only if the light source is small or very distant.

20. The author uses the analogy of the child’s drawing (lines 17-19) primarily in order to

(A) illustrate the ultimate limitation in the precision of sense-data conveyed by quanta

(B) show the sense of helplessness scientists feel in the face of significant observational problems

(C) anticipate the objections of the those scientists who believe that no instrumental aid to observation is entirely reliable

(D) exemplify the similarities between packages of energy and varieties of color（A）

(E) disparage those scientists who believe that measurement by means of quanta offers an accurate picture of the world

21. The author implies that making a sharp division between subject and object in physics is

(A) possible in a measurement o object’s length and position, but not in a measurement of its energy

(B) still theoretically possible in the small-scale world of atoms and electrons

(D) no longer an entirely accurate way to describe observation of the universe（D）

(E) a goal at which scientists still aim

22. The author’s use of the phrase “in a sense” (line 34) implies which of the following?

(A) Quanta of extremely long wavelength are essentially graduated in inches.

(B) quanta of one-inch wavelength are not precisely analogous to yardsticks graduated in inches.

(D) quanta of on-inch wavelength and quanta of extremely long wavelength do not differ only in their wavelengths.（B）

(E) quanta of one-inch wavelength must be measured by different standards than quanta of extremely long wavelength.

23. According to the passage, the quantum theory can be distinguished from previous theories of physics by its

(A) insistence on scrupulously precise mathematical formulations

(B) understanding of the inherent interrelationship of perceiver and perceived

(D) emphasis on small-scale rather than on large-scale phenomena（B）

(E) regard for philosophical issues as well as for strictly scientific ones

Eight percent of the Earth’s

Eight percent of the Earth’s crust is aluminum, and there are hundreds of aluminum-bearing minerals and vast quantities of the rocks that contain them. The best aluminum ore is bauxite, defined as aggregates of aluminous minerals, more or less impure, in which aluminum is present as hydrated oxides. Bauxite is the richest of all those aluminous rocks that occur in large quantities, and it yields alumina, the intermediate product required for the production of aluminum. Alumina also occurs naturally as the mineral corundum, but corundum is not found in large deposits of high purity, and therefore it is an impractical source for making aluminum. Most of the many abundant nonbauxite aluminous minerals are silicates, and, like all silicate minerals, they are refractory, resistant to analysis, and extremely difficult to process. The aluminum silicates are therefore generally unsuitable alternatives to bauxite because considerably more energy is required to extract alumina from them.

17. The author implies that a mineral must either be or readily supply which of the following in order to be classified as an aluminum ore?

(A) An aggregate

(B) Bauxite

(D) Corundum（C）

(E) An aluminum silicate

18. The passage supplies information for answering all of the following questions regarding aluminous minerals EXCEPT:

(A) What percentage of the aluminum in the Earth’s crust is in the form of bauxite?

(B) Are aluminum-bearing nonbauxite minerals plentiful?

(D) Are aluminous hydrated oxides found in rocks?（A）

(E) Do large quantities of bauxite exist?

19. The author implies that corundum would be used to produce aluminum if

(A) corundum could be found that is not contaminated by silicates

(B) the production of alumina could be eliminated as an intermediate step in manufacturing aluminum

(D) new technologies were to make it possible to convert corundum to a silicate（C）

(E) manufacturers were to realize that the world’s supply of bauxite is not unlimited

Diamonds, an occasional component

Diamonds, an occasional component of rare igneous rocks called lamproites and kimberlites, have never been dated satisfactorily. However, some diamonds contain minute inclusions of silicate minerals, commonly olivine, pyroxene, and garnet. These minerals can be dated by radioactive decay techniques because of the very small quantities of radioactive trace elements they, in turn, contain. Usually, it is possible to conclude that the inclusions are older than their diamond hosts, but with little indication of the time interval involved. Sometimes, however, the crystal form of the silicate inclusions is observed to resemble more closely the internal structure of diamond than that of other silicate minerals. It is not known how rare this resemblance is, or whether it is most often seen in inclusions of silicates such as garnet, whose crystallography is generally somewhat similar to that of diamond; but when present, the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic.

17. The author implies that silicate inclusions were most often formed

(A) with small diamonds inside of them

(B) with trace elements derived from their host minerals

(D) at an earlier period than were their host minerals（D）

(E) from the crystallization of rare igneous material

18. According to the passage, the age of silicate minerals included in diamonds can be determined due to a feature of the

(A) trace elements in the diamond hosts

(B) trace elements in the rock surrounding the diamonds

(D) silicate minerals’ crystal structure（C）

(E) host diamonds’ crystal structure

19. The author states that which of the following generally has a crystal structure similar to that of diamond?

(A) Lamproite

(B) Kimberlite

(D) Pyroxene（E）

(E) Garnet

20. The main purpose of the passage is to

(A) explain why it has not been possible to determine the age of diamonds

(B) explain how it might be possible to date some diamonds

(D) compare a method of dating diamonds with a method used to date certain silicate minerals（B）

(E) compare the age of diamonds with that of certain silicate minerals contained within them

Since 1953, many experimental

Since 1953, many experimental attempts to synthesize the chemical constituents of life under “primitive Earth conditions” have been performed, but none of these experiments has produced anything approaching the complexity of the simplest organism. They have demonstrated, however, that a variety of (a variety of: adj.多种的) the complex molecules currently making up living organisms could have been present in the early ocean and atmosphere, with only one limitation: such molecules are synthesized far less readily when oxygen-containing compounds dominate the atmosphere. Therefore some scientists postulate (to assume or claim as true, existent, or necessary: depend upon or start from the postulate of) that the Earth’s earliest atmosphere, unlike that of today, was dominated by hydrogen, methane, and ammonia.

From these studies, scientists have concluded that the surface of the primitive Earth was covered with oceans containing the molecules fundamental to life. Although, at present, scientists cannot explain how these relatively small molecules combined to produce larger, more complex molecules, some scientists have precipitously ventured hypotheses that attempt to explain the development, from lager molecules, of the earliest self-duplicating organisms.

24. According to the passage, which of the following can be inferred about the process by which the chemical constituents of life were synthesized under primitive Earth conditions?

(A) The synthesis is unlikely to occur under current atmospheric conditions.

(B) The synthesis is common in modern laboratories.

(D) The synthesis easily produces the most complex organic molecules.（A）

(E) The synthesis is accelerated by the presence of oxygen-containing compounds.

25. The primary purpose of the passage is to

(A) point out that theories about how life developed on Earth have changed little since 1953

(B) warn of increasing levels of hydrogen, methane, and ammonia in the Earth’s atmosphere

(D) demonstrate that the synthesis of life in the laboratory is too difficult for modern technology（C）

(E) describe how primitive atmospheric conditions produced the complex molecules of living organisms

26. It can be inferred from the passage that “some scientists” assume which of the following concerning “larger, more complex molecules” (line 20)?

(A) The earliest atmosphere was formed primarily of these molecules.

(B) Chemical processes involving these molecules proceeded much more slowly under primitive Earth conditions.

(D) Experimental techniques will never be sufficiently sophisticated to produce in the laboratory simple organisms from these chemical constituents.（C）

(E) Explanations could easily be developed to explain how simple molecules combined to form these more complex ones.

27. The author’s reaction to the attempts that have been made to explain the development of the first self-duplication organisms can best be described as one of

(A) enthusiasm

(B) expectation

(D) skepticism（D）

(E) antipathy

Quantum mechanics (quantum mechanics: n.[物]量子力学) is a highly

Quantum mechanics (quantum mechanics: n.[物]量子力学) is a highly successful theory: it supplies methods for accurately calculating the results of diverse experiments, especially with minute particles. The predictions of quantum mechanics, however, give only the probability of an event, not a deterministic statement of whether or not the event will occur. Because of this probabilism, Einstein remained strongly dissatisfied with the theory throughout his life, though he did not maintain that quantum mechanics is wrong. Rather, he held that it is incomplete: in quantum mechanics the motion of a particle must be described in terms of probabilities, he argued, only because some parameters that determine the motion have not been specified. If these hypothetical “hidden parameters” were known, a fully deterministic trajectory could be defined. Significantly, this hidden-parameter quantum theory leads to experimental predictions different from those of traditional quantum mechanics. Einstein’s ideas have been tested by experiments performed since his death, and as most of these experiments support traditional quantum mechanics, Einstein’s approach is almost certainly erroneous.

24. The author regards the idea that traditional quantum mechanics is incomplete with

(A) approval

(B) surprise

(D) apprehension（E）

(E) skepticism

25. It can be inferred from the passage that the author’s conclusion that Einstein’s approach is “erroneous” (line 22) might have to be modified because

(A) it is theoretically possible to generate plausible theories with hidden parameters within them

(B) some experimental tests of Einstein’s theory do not disconfirm the hidden-parameter theory of quantum mechanics

(D) traditional quantum mechanics has not yet been used to analyze all of the phenomena to which it could be applied（B）

(E) there are too many possible hidden parameters to develop meaningful tests of hidden-parameter theories

26. According to the passage, Einstein posed objections to the

(A) existence of hidden parameters in quantum theory

(B) probabilistic nature of quantum mechanics

(D) results of experiments testing quantum theory（B）

(E) importance accorded quantum mechanics in physics

27. The passage suggests that which of the following would have resulted if the experiments mentioned in lines 18-20 had not supported the predictions of traditional quantum mechanics?

(A) Einstein, had he been alive, would have revised his approach to quantum mechanics.

(B) Hidden-parameter theories would have been considered inaccurate descriptions of real-world phenomena.

(D) Quantum mechanics would have ceased to attract the attention of physicists.（C）

(E) Einstein, had he been alive, would have abandoned attempts to specify the hidden parameters that describe motion.

It is now established that the

It is now established that the Milky Way is far more extended and of much greater mass than was hitherto thought. However, all that is visible of the constituents of the Milky Way’s corona (outer edge), where much of the galaxy’s mass must be located, is a tiny fraction of the corona’s mass. Thus, most of the Milky Way’s outlying matter must be dark.

Why? Three facts are salient. First, dwarf galaxies and globular clusters, into which most of the stars of the Milky Way’s corona are probably bound, consist mainly of old stars. Second, old stars are not highly luminous. Third, no one has detected in the corona the clouds of gaseous matter such as hydrogen and carbon monoxide that are characteristic of the bright parts of a galaxy. At present, therefore, the best explanation—though still quite tentative—for the darkness of the corona is that the corona is composed mainly of old, burned-out stars.

17. The passage as a whole is primarily concerned with

(A) analyzing a current debate

(B) criticizing a well-established theory

(D) stating a conclusion and adducing evidence that may justify it（D）

(E) contrasting two types of phenomena and showing how they are related

18. According to the passage, a bright part of a galaxy typically includes

(A) dwarf galaxies and clusters of stars

(B) a balanced mixture of old and new stars

(D) part of the corona of the galaxy（E）

(E) gases such as hydrogen and carbon monoxide

19. It can be inferred from the passage that, compared with what they now think, until fairly recently astronomers believed that the Milky Way

(A) was much darker

(B) was much smaller

(D) had a much larger corona（B）

(E) had much less gaseous matter

20. The passage presents which of the following as incontrovertible?

I. The low luminosity of old stars

II. The absence of clouds of gaseous matter from the corona of the Milky Way

III. The predominance of globular clusters and dwarf galaxies in the corona of the Milky Way

(A) I only

(B) III only

(D) II and III only（A）

(E) I, II, and III

Analyzing the physics of dance

Analyzing the physics of dance can add fundamentally to a dancer’s skill. Although dancers seldom see themselves totally in physical terms—as body mass moving through space under the influence of well-known forces and obeying physical laws—neither can they afford to ignore the physics of movement. For example, no matter how much a dancer wishes to leap off the floor and then start turning, the law of conservation of angular momentum absolutely prevents such a movement.

Some movements involving primarily vertical or horizontal motions of the body as a whole, in which rotations can be ignored, can be studied using simple equations of linear motion in three dimensions. However, rotational motions require more complex approaches that involve analyses of the way the body’s mass is distributed, the axes of rotation involved in different types of movement, and the sources of the forces that produce the rotational movement.

17. The primary purpose of the passage is to

(A) initiate a debate over two approaches to analyzing a field of study

(B) describe how one field of knowledge can be applied to another field

(D) define and elaborate on an accepted scientific principle（B）

(E) discuss the application of a new theory within a new setting

18. The author mentions all of the following as contributing to an understanding of the physics of dance EXCEPT:

(A) the law of conservation of angular momentum

(B) analyses of the way in which the body’s mass is distributed

(D) analyses of the sources that produce rotational motions（E）

(E) the technical terms for movements such as leaps and turns

19. The author implies that dancers can become more skilled by doing which of the following?

(A) Ignoring rotational movements

(B) Understanding the forces that permit various movements

(D) Learning the technical terms utilized by choreographers（B）

(E) Circumventing the law of conservation of angular momentum

20. Analysis of which of the following would require the kind of complex approach described in lines 14-19?

(A) A long leap across space

(B) A short jump upward with a return to the same place

(D) Short, rapid steps forward and then backward without turning（C）

(E) Quick sidesteps in a diagonal line

The Earth’s magnetic field

The Earth’s magnetic field is generated as the molten iron of the Earth’s outer core revolves around its solid inner core. When surges in the molten iron occur, magnetic tempests are created. At the Earth’s surface, these tempests can be detected by changes in the strength of the Earth’s magnetic field. For reasons not fully understood, the field itself reverses periodically every million years or so (or so: 大约). During the past million years, for instance, the magnetic north pole has migrated between the Antarctic and the Arctic.

Clearly, geophysicists who seek to explain and forecast changes in the field must understand what happens in the outer core. Unlike meteorologists, however, they cannot rely on observations made in their own lifetimes. Whereas atmospheric storms arise in a matter of hours and last for days, magnetic tempests develop over decades and persist for centuries. Fortunately scientists have been recording changes in the Earth’s magnetic field for more than 300 years.

24. In the passage, the author is primarily concerned with

(A) analyzing a complicated scientific phenomenon and its impact on the Earth’s surface features

(B) describing a natural phenomenon and the challenges its study presents to researchers

(D) comparing two distinct fields of physical science and the different research methods employed in each（B）

(E) proposing an explanation for a geophysical phenomenon and an experiment that could help confirm that explanation

25. The passage suggests which of the following about surges in the Earth’s outer core?

(A) They occur cyclically every few decades.

(B) They can be predicted by changes in the Earth’s inner core.

(D) They are linked to disturbances in the Earth’s atmosphere.（C）

(E) They last for periods of about 1 million years.

26. It can be inferred from the passage that geophysicists seeking to explain magnetic tempests ought to conduct research on the Earth’s outer core because the Earth’s outer core

(A) is more fully understood than the Earth’s magnetic field

(B) is more easily observed than the Earth’s magnetic field

(D) is involved in generating the Earth’s magnetic field（D）

(E) reflects changes in the inner core caused by magnetic tempests

27. In the second paragraph, the author is primarily concerned with

(A) stating a limitation that helps determine a research methodology

(B) making a comparative analysis of two different research methodologies

(D) suggesting an optimistic way of viewing a widely feared phenomenon（A）

(E) describing a fundamental issue and discussing its future impact on society

About a century ago, the

About a century ago, the Swedish physical scientist Arrhenius proposed a law of classical chemistry that relates chemical reaction rate to temperature. According to the Arrhenius equation, chemical reactions are increasingly unlikely to occur as temperatures approach absolute zero (absolute zero: n.绝对零度(约为-273.15度)), and at absolute zero (zero degrees Kelvin, or minus 273 degrees Celsius) reactions stop. However, recent experimental evidence reveals that although the Arrhenius equation is generally accurate in describing the kind of chemical reaction that occurs at relatively high temperatures, at temperatures closer to zero a quantum-mechanical effect known as tunneling comes into play; this effect accounts for chemical reactions that are forbidden by the principles of classical chemistry. Specifically, entire molecules can “tunnel” through the barriers of repulsive forces from other molecules and chemically react even though these molecules do not have sufficient energy, according to classical chemistry, to overcome the repulsive barrier.

The rate of any chemical reaction, regardless of the temperature at which it takes place, usually depends on a very important characteristic known as its activation energy. Any molecule can be imagined to reside at the bottom of a so-called potential well of energy. A chemical reaction corresponds to the transition of a molecule from the bottom of one potential well to the bottom of another. In classical chemistry, such a transition can be accomplished only by going over the potential barrier between the wells, the height of which remains constant and is called the activation energy of the reaction. In tunneling, the reacting molecules tunnel from the bottom of one to the bottom of another well without having to rise over the barrier between the two wells. Recently researchers have developed the concept of tunneling temperature: the temperature below which tunneling transitions greatly outnumber Arrhenius transitions, and classical mechanics gives way to its quantum counterpart.

This tunneling phenomenon at very low temperatures suggested my hypothesis about a cold prehistory of life: the formation of rather complex organic molecules in the deep cold of outer space, where temperatures usually reach only a few degrees Kelvin. Cosmic rays (high-energy protons and other particles) might trigger the synthesis of simple molecules, such as interstellar formaldehyde, in dark clouds of interstellar dust. Afterward complex organic molecules would be formed, slowly but surely, by means of tunneling. After I offered my hypothesis, Hoyle and Wickramasinghe argued that molecules of interstellar formaldehyde have indeed evolved into stable polysaccharides such as cellulose and starch. Their conclusions, although strongly disputed, have generated excitement among investigators such as myself who are proposing that the galactic clouds are the places where the prebiological (prebiological: adj.生命起源以前的) evolution of compounds necessary to life occurred.

21. The author of the passage is primarily concerned with

(A) describing how the principles of classical chemistry were developed

(B) initiating a debate about the kinds of chemical reactions required for the development of life

(D) reconciling opposing theories about chemical reactions（C）

(E) clarifying inherent ambiguities in the laws of classical chemistry

22. According to the passage, classical chemical reactions and tunneling reactions are alike in which of the following ways?

(A) In both types of reactions, reacting molecules have to rise over the barrier between the two wells.

(B) In both types of reactions, a transition is made from the bottom of one potential well to the bottom of another.

(D) In neither type of reaction does the rate of a chemical reaction depend on its activation energy.（B）

(E) In both types of reactions, reacting molecules are able to go through the barrier between the two wells.

23. According to the Arrhenius equation as discussed in the passage, which of the following statements about chemical reactions is true?

(A) Chemical reactions are less likely to occur at temperatures close to absolute zero.

(B) In some cases the rate of a chemical reaction is related to temperature and in other cases it is not.

(D) The rate of a chemical reaction depends on many other factors besides temperature.（A）

(E) Chemical reaction rate and temperature are not related.

24. The author’s attitude toward the theory of a cold pre-history of life can best be described as

(A) neutral

(B) skeptical

(D) very supportive（C）

(E) pointedly critical

25. The author’s hypothesis concerning the cold prehistory of life would be most weakened if which of the following were true?

(A) Cosmic rays are unlikely to trigger the formation of simple molecules.

(B) Tunneling occurs only in a narrow band of temperatures around zero degrees Kelvin.

(D) Simple molecules can be synthesized by means of tunneling.（A）

(E) Classical chemical reactions do not occur at temperatures close to absolute zero.

26. Which of the following best describes the hypothesis of Hoyle and Wickramasinghe as it is presented in the passage?

(A) Cosmic rays can directly synthesize complex organic molecules.

(B) The galactic clouds are the places where prebiological evolution of compounds necessary to life occurred.

(D) Molecules of interstellar formaldehyde can evolve into complex organic molecules.（D）

(E) Complex organic molecules can be synthesized from stable polysaccharides such as cellulose and starch.

27. Which of the following best describes the organization of the first two paragraphs of the passage?

(A) The author cites a basic principle of classical chemistry and then describes the research from which that principle was developed.

(B) The author cites an apparent contradiction to the principles of classical chemistry and then explains the process of a chemical reaction to show there is in fact no contradiction.

(D) The author presents a law of classical chemistry in order to introduce a kind of chemical reaction that differs from it and then explains the essential difference between the two.（D）

(E) The author presents the fundamental rules of classical chemistry in order to introduce an explanation of a specific chemical reaction.

Many philosophers disagree

Many philosophers disagree over the definition of morality, but most disputants fall into (fall into: v.分成, 属于) one of two categories: egocentrics, who define morality as the pursuit of self-fulfillment, and sociocentrics, who define morality as an individual’s obligations to society. Where does the truth lie? Fortunately, the stem of the word “morality” provides some clues. The word “mores” originally referred to the customs of preliterate cultures. Mores, which embodied each culture’s ideal principles for governing every citizen, were developed in the belief that the foundation of a community lies in the cultivation of individual powers to be placed in service to the community. These mores were concerned with such skills as food-gathering and warfare as well as an individual’s relationships with others. Thus, I submit (intransitive senses: to defer to or consent to abide by the opinion or authority of another), “morality” must be concerned with what is honored by the community at large (at large: adv.未被捕, 详尽, 普遍). However, self-fulfillment is important to morality because unfulfilled citizens, no matter how virtuous, cannot perform the duties morality assigns them.

17. The primary purpose of this passage is to

(A) summarize an argument

(B) resolve a dispute

(D) prove a hypothesis（B）

(E) initiate a debate

18. According to the passage, mores in preliterate cultures concerned such skills as warfare and food-gathering because these skills were

(A) characteristic of an individual’s self-fulfillment

(B) examples of a culture’s traditions

(D) demonstrations of an individual’s contributions to the community（D）

(E) examples of a community’s governing principles

19. It can be inferred from the passage that the author would be most likely to agree with which of the following statements regarding sociocentrics and egocentrics?

(A) The position of the sociocentrics is stronger than that of the egocentrics.

(B) The positions of the egocentrics and sociocentrics are of equal merit.

(D) Neither position contributes very much to an understanding of the definition of morality.（A）

(E) The dispute between the egocentrics and sociocentrics is based on trivial issues.

20. With which of the following statements regarding the relationship between the individual and morality would the author be most likely to agree?

(A) Failure in social obligations is the price of success in individual endeavors.

(B) The unfulfilled citizen cannot fulfill his moral obligations to the community.

(D) The unfulfilled citizen is without virtue.（B）

(E) Wealth harms a citizen’s moral standing in the community.

For many years, Benjamin

For many years, Benjamin Quarles’ seminal account of the participation of African Americans in the American Revolution has remained the standard work in the field. According to Quarles, the outcome of this conflict was mixed for African American slaves who enlisted in Britain’s fight against its rebellious American colonies in return for (in return for: adv.作为...的报答) the promise of freedom: the British treacherously resold many into slavery in the West Indies (the islands lying between SE N. America & N S. America bordering the Caribbean & comprising the Greater Antilles, Lesser Antilles, & Bahamas), while others obtained freedom in Canada and Africa. Building on Quarles’ analysis of the latter group, Sylvia Frey studied the former slaves who emigrated to British colonies in Canada. According to Frey, these refugees—the most successful of the African American Revolutionary War participants—viewed themselves as the ideological heirs of the American Revolution. Frey sees this inheritances reflected in their demands for the same rights that the American revolutionaries had demanded from the British: land ownership, limits to arbitrary authority and burdensome taxes, and freedom of religion.

17. According to the passage, which of the following is true about the African American Revolutionary War participants who settled in Canada after the American Revolution?

(A) Although they were politically unaligned with either side, they identified more with British ideology than with American ideology.

(B) While they were not immediately betrayed by the British, they ultimately suffered the same fate as did African American Revolutionary War participants who were resold into slavery in the West Indies.

(D) They were more politically active than were African American Revolutionary War participants who settled in Africa.（E）

(E) They were more successful than were African American Revolutionary War participants who settled Africa.

18. Which of the following is most analogous to the relationship between the African American Revolutionary War participants who settled in Canada after the American Revolution and the American revolutionaries, as that relationship is described in the passage?

(A) A brilliant pupil of a great musician rebels against the teacher, but adopts the teacher’s musical style after the teacher’s unexpected death.

(B) Two warring rulers finally make peace after a lifetime of strife when they realize that they have been duped by a common enemy.

(C) A child who has sided with a domineering parent against a defiant sibling later makes demands of the parent similar to those once made by the sibling.

(D) A writer spends much of her life popularizing the work of her mentor, only to discover late in life that much of the older writer’s work is plagiarized from the writings of a foreign contemporary.（C）

(E) Two research scientists spend much of their careers working together toward a common goal, but later quarrel over which of them should receive credit for the training of a promising student.

19. The author of the passage suggests that which of the following is true of Benjamin Quarles’ work?

(A) It introduced a new and untried research methodology.

(B) It contained theories so controversial that they gave rise to an entire generation of scholarship.

(D) It launched the career of a scholar who later wrote even more important works.（C）

(E) At the time it appeared, its author already enjoyed a well-established reputation in the field.

20. Which of the following can be inferred from the passage concerning Britain’s rule in its Canadian colonies after the American Revolution?

(A) Humiliated by their defeat by the Americans, the British sharply curtailed civil rights in their Canadian colonies.

(B) The British largely ignored their Canadian colonies.

(C) The British encouraged the colonization of Canada by those African Americans who had served on the American side as well as by those who had served on the British side.

(D) Some of Britain’s policies in its Canadian colonies were similar to its policies in its American colonies before the American Revolution.（D）

(E) To reduce the debt incurred during the war, the British imposed even higher taxes on the Canadian colonists than they had on the American colonists.

1 ... 7 8 9 10 11 12 13 14 ... 99