1、GRE-练习二十及答案解析(总分：100.00，做题时间：90 分钟)一、BIndefinite item(总题数：27，分数：100.00)1.If a supernova (the explosion of a massive star) triggered star formation from dense clouds of gas and dust, and if the most massive star to be formed from the cloud evolved into a supernova and triggered a new round of star fo
2、rmation, and so on, then a chain of star-forming regions would result. If many such chains were created in a differentially rotating galaxy, the distribution of stars would resemble the observed distribution in a spiral galaxy.This line of reasoning underlies an Uexciting/U new theory of spiral-gala
3、xy structure. A computer simulation based on this theory has reproduced the appearance of many spiral galaxies without assuming an underlying density wave, the hallmark of the most widely accepted theory of the large-scale structure of spiral galaxies. That theory maintains that a density wave of sp
4、iral form sweeps through the central plane of a galaxy, compressing clouds of gas and dust, which collapse into stars that form a spiral pattern. The authors attitude toward the new theory of spiral-galaxy structure can best be described as A. euphoric. B. enthusiastic. C. concerned. D. critical. E.
5、 disputatious.（分数：4.00）A.B.C.D.E.2.A mysterious phenomenon is the ability of over-water migrants to travel on course. Birds, bees, and other species can keep track of time without any sensory cues from the outside world, and such “biological clocks“ clearly contribute to their “compass sense“. For e
6、xample, they can use the position of the Sun or stars, along with the time of day, to find north. But compass sense alone cannot explain how birds navigate the ocean: after a flock traveling east is blown far south by a storm, it will assume the proper northeasterly course to compensate. Perhaps, so
7、me scientists thought, migrants determine their Ugeographic position on Earth by celestial navigation/U, almost as human navigators use stars and planets, Ubut this would demand of the animals a fantastic map sense./U Researchers now know that some species have a magnetic sense, which might allow mi
8、grants to determine their geographic location by detecting variations in the strength of the Earths magnetic field.In maintaining that migrating animals would need “a fantastic map sense“ to determine their geographic position by celestial navigation, the author intends to express A. admiration for
9、the ability of the migrants. B. skepticism about celestial navigation as an explanation. C. certainty that the phenomenon of migration will remain mysterious. D. interest in a new method of accounting for over-water migration. E. surprise that animals apparently navigate in much the same way that hu
10、man beings do.（分数：4.00）A.B.C.D.E.3.Tocqueville, apparently, was wrong. Jacksonian America was not a fluid, egalitarian society where individual wealth and poverty were ephemeral conditions. At least so argues E. Pessen in his iconoclastic study of the very rich in the United States between 1825 and
11、1850.Pessen does present a quantity of examples, together with some Urefreshingly intelligible statistics,/U to establish the existence of an inordinately wealthy class. Though active in commerce or the professions, most of the wealthy were not self-made, but had inherited family fortunes. In no sen
12、se mercurial, these great fortunes survived the financial panics that destroyed lesser ones. Indeed, in several cities the wealthiest one percent constantly increased its share until by 1850 it owned half of the communitys wealth. Although these observations are true, Pessen overestimates their impo
13、rtance by concluding from them that the undoubted progress toward inequality in the late eighteenth century continued in the Jacksonian period and that the United States was a class-ridden, plutocratic society even before industrialization.The authors attitude toward Pessens presentation of statisti
14、cs can be best described as A. disapproving B. shocked C. suspicious D. amused E. laudatory（分数：4.00）A.B.C.D.E.4.The intensive work of materials scientists and solid-state physicists has given rise to a class of solids known as amorphous metallic alloys, or glassy metals. There is a growing interest
15、among theoretical and applied researchers alike in the structural properties of these materials.When a molten metal or metallic alloy is cooled to a solid, a crystalline structure is formed that depends on the particular alloy composition. In contrast, molten nonmetallic glass-forming materials, whe
16、n cooled, do not assume a crystalline structure, but instead retain a structure somewhat like that of the liquidan amorphous structure. At room temperature, the natural long-term tendency for both types of materials is to assume the crystalline structure. The difference between the two is in the kin
17、etics or rate of formation of the crystalline structure, which is controlled by factors such as the nature of the chemical bonding and the ease with which atoms move relative to each other. Thus, in metals, the kinetics favors rapid formation of a crystalline structure, whereas in nonmetallic glasse
18、s the rate of formation is so slow that almost any cooling rate is sufficient to result in an amorphous structure. For glassy metals to be formed, the molten metal must be cooled extremely rapidly so that crystallization is suppressed.The structure of glassy metals is thought to be similar to that o
19、f liquid metals. One of the first attempts to model the structure of a liquid was that by the late J.D. Bernal of the University of London, who packed hard spheres into a rubber vessel in such a way as to obtain the maximum possible density. The resulting dense, random-packed structure was the basis
20、 for many attempts to model the structure of glassy metals. Calculations of the density of alloys based on Bernal-type models of the alloys metal component agreed fairly well with the experimentally determined values from measurements on alloys consisting of a noble metal together with a metalloid,
21、such as alloys of palladium and silicon, or alloys consisting of iron, phosphorus, and carbon, although small discrepancies remained. One difference between real alloys and the hard spheres used in Bernal models is that the components of an alloy have different sizes, so that models based on two siz
22、es of spheres are more appropriate for a binary alloy, for example, the smaller metalloid atoms of the alloy might fit into holes in the dense, random-packed structure of the larger metal atoms.One of the most promising properties of glassy metals is their high strength combined with high malleabili
23、ty. In usual crystalline materials, one finds an inverse relation between the two properties, whereas for many practical applications simultaneous presence of both properties is desirable. UOne residual obstacle to practical applications that is likely to be overcome is the fact that glassy metals w
24、ill crystallize at relatively low temperatures when heated slightly./UThe authors attitude toward the prospects for the economic utilization of glassy metals is one of _. A. disinterest B. impatience C. optimism D. apprehension E. skepticism（分数：4.00）A.B.C.D.E.5.When the same parameters and quantitat
25、ive theory are used to analyze both termite colonies and troops of rhesus macaques, we will have a unified science of sociobiology. Can this ever really happen? As my own studies have advanced, UI have been increasingly impressed/U with the functional similarities between insect and vertebrate socie
26、ties and less so with the structural differences that seem, at first glance, to constitute such an immense gulf between them. Consider for a moment termites and macaques. Both form cooperative groups that occupy territories. In both kinds of society there is a well-marked division of labor. Members
27、of both groups communicate to each other hunger, alarm, hostility, caste status or rank, and reproductive status. From the specialists point of view, this comparison may at first seem facileor worse. But it is out of such deliberate oversimplification that the beginnings of a general theory are made
28、.The authors attitude toward the possibility of a unified theory in sociobiology is best described as which of the following? A. Guarded optimism. B. Unqualified enthusiasm. C. Objective indifference. D. Resignation. E. Dissatisfaction.（分数：4.00）A.B.C.D.E.6.Although the development of new infrastruct
29、ure (such public facilities as power plants, schools, and bridges) is usually determined by governmental planning, Usometimes this development can be planned more flexibly and realistically by private investors/U who anticipate profit from the collection of user fees. Such profits can contribute to
30、the financing of more infrastructure if demand proves great enough, whereas the reluctance of developers to invest in such projects can signal that additional infrastructure is not needed. During the economic boom of the 1980s, for example, the state of Virginia authorized private developers to buil
31、d a $300 million toll road.The passage implies that the “governmental planning“ mentioned in line 4 may lead to which of the following problems? A. Improper use of profits derived from user fees. B. Unduly slow development of necessary new infrastructure. C. Unrealistic decisions about developing ne
32、w infrastructure. D. Incorrect predictions about profits to be gained from user fees. E. Obstruction of private financing for the development of new infrastructure.（分数：4.00）A.B.C.D.E.7.Allen and Wolkowitzs research in 1978 challenges the common claim that homeworkwaged labor performed at home for a
33、companyis primarily a response to women workers needs and preferences. UBy focusing on a limited geographical area in order to gather in-depth information, Allen and Wolkowitz have avoided the methodological pitfalls/U that have plagued earlier research on homework. Their findings disprove accepted
34、notions about homeworkers: that they are unqualified for other jobs and that they use homework as a short-term strategy for dealing with child care.The passage suggests which of the following about research on homework before 1978? A. It was conducted primarily with women who did not have extensive
35、household responsibilities or care for small children at home. B. It was conducted with homeworkers and companies over a large geographical area. C. It indicated that women homeworkers had numerous opportunities to work outside the home. D. It indicated that homeworkers usually work for companies th
36、at are close to their homes. E. It indicated that homework was financially advantageous to large companies.（分数：4.00）A.B.C.D.E.8.The origin of the theory that major geologic events may occur at regular intervals can be traced back not to a study of volcanism or plate tectonics but to an investigation
37、 of marine extinctions. In the early 1980s, scientists began to look closely at the question of how these extinctions occur. Two paleontologists, Raup and Sepkoski, compiled a master list of marine species that died out during the past 268 million years and noted that there were brief periods during
38、 which many species disappeared at once. These mass extinctions occurred at surprisingly regular intervals.Later studies revealed that extinctions of terrestrial reptiles and mammals also occurred periodically. UThese findings, combined with the research of Raup and Sepkoski, led scientists to hypot
39、hesize the existence of some kind of cyclically recurring force powerful enough to affect living things profoundly./U Speculation that so powerful a Uforce/U might affect geologic events as well led geologists to search for evidence of periodicity in episodes of volcanism, seafloor spreading, and pl
40、ate movement.The passage suggests which of the following about the “force“ highlighted in the passage? A. It is responsible for most of the major geologic events that have occurred. B. It is responsible for most of the marine extinctions that have occurred. C. Its recurrence is unlikely to be able t
41、o be predicted by scientists. D. Its existence was not seriously considered by scientists before Raup and Sepkoski did their research. E. Its existence was confirmed by the research of Raup and Sepkoski.（分数：4.00）A.B.C.D.E.9.Several things, however, suggest that the conventional view needs revising.
42、For example, the genus Lingula has an unbroken fossil record extending over more than half a billion years to the present. Thus, if longevity is any measure, brachiopods are the most successful organisms extant. UFurther, recent studies suggest that diversity among species is a less important measur
43、e of evolutionary success/U than is the ability to withstand environmental change, such as when a layer of clay replaces sand on the ocean bottom. The relatively greater uniformity among the existing brachiopod species may offer greater protection from environmental change and hence may reflect high
44、ly successful adaptive behavior.It can be inferred from the passage that the conventional view is that a large diversity among species of a given class of organisms typically leads to which of the following? A. Difficulty in classification. B. A discontinuous fossil record. C. A greater chance of su
45、rvival over time. D. Numerical abundance. E. A longer fife span.（分数：4.00）A.B.C.D.E.10.UWhen literary periods are defined on the basis of mens writing, womens writing must be forcibly assimilated into an irrelevant grid:/U a Renaissance that is not a renaissance for women, a Romantic period in which
46、women played very little part, a modernism with which women conflict Simultaneously, the history of womens writing has been suppressed, leaving large, mysterious gaps in accounts of the development of various genres. Feminist criticism is beginning to correct this situation. Margaret Anne Doody, for
47、 example, suggests that during “the period between the death of Richardson and the appearance of the novels of Scott and Austen,“ which has “been regarded as a dead period,“ late-eighteenth-century women writers actually developed “the paradigm for womens fiction of the nineteenth centurysomething h
48、ardly less than the paradigm of the nineteenth-century novel itself.“ Feminist critics have also pointed out that the twentieth-century writer Virginia Woolf belonged to a tradition other than modernism and that this tradition surfaces in her work precisely where criticism has hitherto found obscuri
49、ties, evasions, implausibilities, and imperfections.It can be inferred from the passage that the author views the division of literature into periods based on mens writing as an approach that A. makes distinctions among literary periods ambiguous. B. is appropriate for evaluating only premodern literature. C. was misunderstood until the advent of feminist criticism. D. pro
