gre考试阅读真题解析(A)

　　Aided by the recent ability to analyze samples of air trapped in glaciers, scientists now have a clearer idea of the relationship between atmospheric composition and global temperature change over the past 160,000 years. In particular, determination of atmospheric composition during periods of glacial expansion and retreat is possible using data from the 2,000 meter Vostok ice core drilled in Antarctica. The technique involved is similar to that used in analyzing cores of marine sediments, where the ratio of the two common isotopes of oxygen, 18O and 16O, accurately reflects past temperature changes. Isotopic analysis of oxygen in the Vostok core suggests mean global temperature fluctuations of up to 10 degrees centigrade over the past 160,000 years.

　　Data from the Vostok core also indicate that the amount of carbon dioxide has fluctuated with temperature over the same period: the higher the temperature, the higher the concentration of carbon dioxide and the lower the temperature, the lower the concentration. Although change in carbon dioxide content closely follows change in temperature during periods of deglaciation, it apparently lags behind temperature during periods of cooling. The correlation of carbon dioxide with temperature, of course, does not establish whether changes in atmospheric composition caused the warming and cooling trends or were caused by their.

　　The correlation between carbon dioxide and temperature throughout the Vostok record is consistent and predictable. The absolute temperature changes, however, are from 5 to 14 times greater than would be expected on the basis of carbon dioxides own ability to absorb infrared radiation, or radiant heat. This reaction suggests that, quite aside from changes in heat-trapping gases, commonly known as greenhouse gases, certain positive feedbacks are also amplifying the temperature change. Such feedbacks might involve ice on land and sea, clouds, or water vapor, which also absorb radiant heat .

　　Other data from the Vostok core show that methane gas also correlates closely with temperature and carbon dioxide. The methane concentration nearly doubled, for example, between the peak of the penultimate glacial period and the following interglacial period. Within the present interglacial period it has more than doubled in just the past 300 years and is rising rapidly. Although the concentration of atmospheric methane is more than two orders of magnitude lower than that of carbon dioxide, it cannot be ignored: the radiative properties of methane make it 20 times more effective, molecule for molecule, than carbon dioxide in absorbing radiant heat. On the basis of a simulation model that climatological researchers have developed, methane appears to have been about 25 percent as important as carbon dioxide in the warming that took place during the most recent glacial retreat 8,000 to 10,000 years ago.

　　17. The primary purpose of the passage is to

　　 interpret data

　　 explain research methodology

　　 evaluate a conclusion

　　 suggest a new technique

　　 attack a theory

　　18. According to the passage, which of the following statements about methane is true?

　　 Methane is found in marine sediments.

　　 Methane is more effective than carbon dioxide in absorbing radiant heat.

　　 The Earths atmosphere now contains more than twice as much methane as it does carbon dioxide.

　　 The higher the concentration of carbon dioxide in the Earths atmosphere, the lower the concentration of methane.

　　 Most of the global warming that has occurred during the past 10 years has been associated with increased methane concentration.

　　19. According to the passage, which of the following statements best describes the relationship between carbon dioxide and global temperature?

　　 Carbon dioxide levels change immediately in response to changes in temperature.

　　 Carbon dioxide levels correlate with global temperature during cooling periods only.

　　 Once carbon dioxide levels increase, they remain high regardless of changes in global temperature.

　　 Carbon dioxide levels increase more quickly than global temperature does.

　　 During cooling periods, carbon dioxide levels initially remain high and then decline.

　　20. The author mentions certain positive feedbacks in order to indicate that

　　 increased concentration of carbon dioxide in the Earths atmosphere is responsible for global temperature increase

　　 some climate simulation models have produced useful information

　　 greenhouse gases alone do not account for global temperature increase

　　 variables that benefit life are causing global temperature to increase

　　 beneficial substances that are not heat-trapping gases and that contribute to global temperature increase have been found in the Vostok ice core

　　21. It can be inferred from the passage that a long-term decrease in the concentration of carbon dioxide in the Earths atmosphere would

　　 increase methane concentration in the Earths atmosphere

　　 accompany a period of glaciation

　　 encourage the formation of more oxygen isotopes in the Earths atmosphere

　　 promote the formation of more water in the Earths global environment

　　 increase the amount of infrared radiation absorbed by the Earths atmosphere

　　22. The passage suggests that when the methane concentration in the Earths atmosphere decreases, which of the following also happens?

　　 Glaciers melt faster.

　　 The concentration of carbon dioxide increases.

　　 The mean global temperature decreases.

　　 Carbon dioxide absorbs more radiant beat.

　　 More clouds form in the Earths atmosphere.

　　23. In the fourth paragraph, the author is primarily concerned with

　　 restating the main idea of the passage

　　 using research findings to develop a simulation model

　　 outlining the direction of future reserves

　　 providing an additional example of a phenomenon

　　 introducing a conflicting hypothesis

　　In The Women of Mexico City, 1796-1857, Sylvia Marina Arrom argues that the status of women in Mexico City improved during the nineteenth century. According to Arrom, households headed by females and instances of women working outside the home were much more common than scholars have estimated; efforts by the Mexican government to encourage female education resulted in increased female literacy; and influential male writers wrote pieces advocating education, employment, and increased family responsibilities for women, while deploring womens political and marital inequality. Mention of the fact that the civil codes of 1870 and 1884 significantly advanced womens rights would have further strengthened Arroms argument.

　　Arrom does not discuss whether womens improved status counteracted the effects on women of instability in the Mexican economy during the nineteenth century. However, this is not so much a weakness in her work as it is the inevitable result of scholars neglect of this period. Indeed, such gaps in Mexican history are precisely what make Arroms pioneering study an important addition to Latin American womens history.

　　24. The passage is primarily concerned with doing which of the following?

　　 Reviewing a historical study of the status of women in Mexico City during the nineteenth century

　　 Analyzing the effects of economic instability on the status of women in Mexico during the nineteenth century

　　 Advancing a thesis explaining why womens status in Mexico City improved during the nineteenth century

　　 Rejecting the thesis that the status of women in Mexico City during the nineteenth century actually improved

　　 Praising an author for a pioneering attempt to bridge significant gaps in Mexicos economic history prior to 1790

　　25. According to the author of the passage, Arroms study can be characterized as an important addition to Latin American womens history because it

　　 offers a radical thesis concerning the status of womens civil rights in Mexican society during the nineteenth century

　　 relies on a new method of historical analysis that has not previously been applied to Latin American history

　　 focuses only on the status of women in Mexican society

　　 addresses a period in Mexican history that scholars have to some extent 有一点) neglected

　　 is the first study to recognize the role of the Mexican government in encouraging womens education

　　26. It can be inferred from the passage that Arrom would agree with which of the following assertions?

　　 Efforts by the Mexican government to encourage education for women during the nineteenth century were hampered by the economic instability of that period.

　　 The most significant advances in the rights of Mexican women during the nineteenth century occurred prior to 1857.

　　 Improvements in the status of women in Mexico City during the nineteenth century were accompanied by similar improvements in the status of women in other large Latin American cities.

　　 Scholars have in the past accorded the most significance to nineteenth-century Mexican literature that supported the status quo in womens political and marital rights.

　　 Scholars have in the past underestimated the number of households headed by females in Mexico City.

　　27. Which of the following best describes the authors attitude toward Arroms work?

　　 Uncritical approval

　　 Enthusiasm tempered by minor reservations

　　 Praise for her thesis, despite skepticism regarding the sources of her evidence

　　 Reluctant acceptance, despite lingering doubts regarding the accuracy of her thesis

　　 Rejection, despite admiration for her attempt to break new ground in a hitherto neglected field

答案：17-27：ABECBCDADEB