gre阅读练习每日一篇(二十六)

　　掌握了gre阅读里的长难句，到了实战演习的时候了。gre阅读练习每日一篇帮助gre考生循序渐进地进行练习和总结。希望gre考生在进行gre阅读练习时，也按着考试时候的时间规定自己的练习，这样才能有效果。

　　The molecules of carbon dioxide in the Earths atmosphere affect the heat balance of the Earth by acting as a one-way screen. Although these molecules allow radiation at visible wavelengths, where most of the energy of sunlight is concentrated, to pass through, they absorb some of the longer-wavelength, infrared emissions radiated from the Earths surface, radiation that would otherwise be transmitted back into space. For the Earth to maintain a constant average temperature, such emissions from the planet must balance incoming solar radiation. If there were no carbon dioxide in the atmosphere, heat would escape from the Earth much more easily. The surface temperature would be so much lower that the oceans might be a solid mass of ice.

　　Today, however, the potential problem is too much carbon dioxide. The burning of fossil fuels and the clearing of forests have increased atmospheric carbon dioxide by about 15 percent in the last hundred years, and we continue to add carbon dioxide to the atmosphere. Could the increase in carbon dioxide cause a global rise in average temperature, and could such a rise have serious consequences for human society? Mathematical models that allow us to calculate the rise in temperature as a function of the increase indicate that the answer is probably yes.

　　Under present conditions a temperature of-18℃ can be observed at an altitude of 5 to 6 kilometers above the Earth. Below this altitude , the temperature increases by about 6℃ per kilometer approaching the Earths surface, where the average temperature is about 15℃. An increase in the amount of carbon dioxide means that there are more molecules of carbon dioxide to absorb infrared radiation. As the capacity of the atmosphere to absorb infrared radiation increases, the radiating level and the temperature of the surface must rise.

　　One mathematical model predicts that doubling the atmospheric carbon dioxide would raise the global mean surface temperature by 2.5℃. This model assumes that the atmospheres relative humidity remains constant and the temperature decreases with altitude at a rate of 6.5℃ per kilometer. The assumption of constant relative humidity is important, because water vapor in the atmosphere is another efficient absorber of radiation at infrared wavelengths. Because warm air can hold more moisture than cool air, the relative humidity will be constant only if the amount of water vapor in the atmosphere increases as the temperature rises. Therefore, more infrared radiation would be absorbed and reradiated back to the Earths surface. The resultant warming at the surface could be expected to melt snow and ice, reducing the Earths reflectivity. More solar radiation would then be absorbed, leading to a further increase in temperature.

　　17. The primary purpose of the passage is to

　　 warn of the dangers of continued burning of fossil fuels

　　 discuss the significance of increasing the amount of carbon dioxide in the atmosphere

　　 explain how a constant temperature is maintained on the Earths surface

　　 describe the ways in which various atmospheric and climatic conditions contribute to the Earths weather

　　 demonstrate the usefulness of mathematical models in predicting long-range climatic change

　　18. According to the passage, the greatest part of the solar energy that reaches the Earth is

　　 concentrated in the infrared spectrum

　　 concentrated at visible wavelengths

　　 absorbed by carbon dioxide molecules

　　 absorbed by atmospheric water vapor

　　 reflected back to space by snow and ice

　　19. According to the passage, atmospheric carbon dioxide performs all of the following functions EXCEPT:

　　 absorbing radiation at visible wavelengths

　　 absorbing infrared radiation

　　 absorbing outgoing radiation from the Earth

　　 helping to retain heat near the Earths surface

　　 helping to maintain a constant average temperature on the Earths surface

　　20. Which of the following best describes the authors attitude toward the increasing amount of carbon dioxide in the atmosphere and its consequences?

　　 Incredulous

　　 Completely detached

　　 Interested but skeptical

　　 Angry yet resigned

　　 Objective yet concerned

　　21. It can be concluded from information contained in the passage that the average temperature at an altitude of 1 kilometer above the Earth is about

　　 15℃

　　 9℃

　　 2.5℃

　　 -12℃

　　 -18℃

　　22. It can be inferred from the passage that the construction of the mathematical model mentioned in the passage involved the formulation of which of the following?

　　 An assumption that the amount of carbon dioxide added to the atmosphere would in reality steadily increase

　　 An assumption that human activities are the only agencies by which carbon dioxide is added to the atmosphere

　　 Assumptions about the social and political consequences of any curtailment of the use of fossil fuels

　　 Assumptions about the physical conditions that are likely to prevail during the period for which the model was made

　　 Assumptions about the differential behavior of carbon dioxide molecules at the various levels of temperature calculated in the model

　　23. According to the passage, which of the following is true of the last hundred years?

　　 Fossil fuels were burned for the first time.

　　 Greater amounts of land were cleared than at any time before.

　　 The average temperature at the Earths surface has become 2℃ cooler.

　　 The amount of carbon dioxide in the atmosphere has increased measurably.

　　 The amount of farmland worldwide has doubled.

　　Some modern anthropologists hold that biological evolution has shaped not only human morphology but also human behavior. The role those anthropologists ascribe to evolution is not of dictating the details of human behavior but one of imposing constraintsways of feeling, thinking, and acting that come naturally in archetypal situations in any culture. Our frailtiesemotions and motives such as rage, fear, greed, gluttony, joy, lust, lovemay be a very mixed assortment, but they share at least one immediate quality: we are, as we say, in the grip of them. And thus they give us our sense of constraints.

　　Unhappily, some of those frailtiesour need for ever-increasing security among themare presently maladaptive. Yet beneath the overlay of cultural detail, they, too, are said to be biological in direction, and therefore as natural to us as are our appendixes. We would need to comprehend thoroughly their adaptive origins in order to understand how badly they guide us now. And we might then begin to resist their pressure.

　　24. The primary purpose of the passage is to present

　　 a position on the foundations of human behavior and on what those foundations imply

　　 a theory outlining the parallel development of human morphology and of human behavior

　　 a diagnostic test for separating biologically determined behavior patterns from culture-specific detail

　　 a practical method for resisting the pressures of biologically determined drives

　　 an overview of those human emotions and motives that impose constraints on human behavior

　　25. The author implies that control to any extent over the frailties that constrain our behavior is thought to presuppose

　　 that those frailties are recognized as currently beneficial and adaptive

　　 that there is little or no overlay of cultural detail that masks their true nature

　　 that there are cultures in which those frailties do not come naturally and from which such control can be learned

　　 a full understanding of why those frailties evolved and of how they function now

　　 a thorough grasp of the principle that cultural detail in human behavior can differ arbitrarily from society to society

　　26. Which of the following most probably provides an appropriate analogy from human morphology for the details versus constraints distinction made in the passage in relation to human behavior?

　　 The ability of most people to see all the colors of the visible spectrum as against most peoples inability to name any but the primary colors

　　 The ability of even the least fortunate people to show compassion as against peoples inability to mask their feelings completely

　　 The ability of some people to dive to great depths as against most peoples inability to swim long distances

　　 The psychological profile of those people who are able to delay gratification as against peoples inability to control their lives completely

　　 The greater lung capacity of mountain peoples that helps them live in oxygen-poor air as against peoples inability to fly without special apparatus

　　27. It can be inferred that in his discussion of maladaptive frailties the author assumes that

　　 evolution does not favor the emergence of adaptive characteristics over the emergence of maladaptive ones

　　 any structure or behavior not positively adaptive is regarded as transitory in evolutionary theory

　　 maladaptive characteristics, once fixed, make the emergence of other maladaptive characteristics more likely

　　 the designation of a characteristic as being maladaptive must always remain highly tentative

　　 changes in the total human environment can outpace evolutionary change

答案：17-27：BBAEBDDADEE