南京林业大学往年考博英语样题

2015-07-31 17:25:00来源：网络

　　Passage 4

　　Scientists studying the effect of large volcanic eruptions on global climate have long focused on the major quantities of carbon dioxide(CO2), a gas known to contribute to the greenhouse effect, produced by these eruptions. It is well observed that such greenhouse gases trap heat radiated from the surface of the earth, thereby forming a type of insulation around the planet. The greenhouse effect is essential for ecological equipoise because it maintains the temperature of the planet within habitable parameters, but there is growing concern that man-made production of gases such as CO2 from the burning of fossil fuels may be threatening the system’s tolerance, and have resulted in excessive warming on a global scale.

　　While volcanic eruptions indubitably metabolize and accumulate CO2 in the atmosphere, it has been recently discovered that their impact is virtually trivial compared to the quantity produced by human activities, especially heavy industry. In reality, the more substantive climatic effect from volcanoes results from the production of atmospheric haze, whereby large eruption columns inject ash particles and sulfur-rich gases into the troposphere and stratosphere, clouds that circumscribe the globe within weeks of the volcanic activity. Ash and aerosol clouds from large volcanic eruptions disseminate quickly through the atmosphere, and the small ash particles decrease the amount of sunlight reaching the surface of the earth and lower average global temperatures, while the sulfurous gases combine with water in the atmosphere to form acidic aerosols that also absorb incoming solar radiation and scatter it back out into space.

　　There is evidence that volcanoes’ stratospheric ash clouds has a lesser effect on global temperatures than aerosol clouds, given that the major Mt. St. Helens eruption had lowered global temperatures by about 0.1 degree Celsius, while two years later the much smaller eruption of El Chico had, by contrast, three to five times the global cooling effect worldwide. Despite its smaller ash cloud, El Chico emitted more than 40 times the volume of sulfur-rich gases produced by Mt. St. Helens, revealing that the formation of atmospheric sulfur aerosols has a more substantial effect on global temperatures than simply the volume of ash produced during an eruption. Sulfate aerosols appear to necessitate several years to settle out of the atmosphere, one of the reasons their effects are so widespread and enduring. This corroborates the opinion of those scientists who argue that without the cooling effect of major volcanic eruptions such as El Chico, global warming effects caused by human activities would be far more substantial. It should be noted that major volcanic eruptions have additional climatic effects beyond global temperature decreases and acid rain, for ash and aerosol particles suspended in the atmosphere scatter light of red wavelengths, often resulting in brilliantly colored sunsets and sunrises around the world.

　　19. According to the passage, scientists have decided that sulfur aerosols from volcanic eruptions affect global temperatures to a greater extent than ash clouds because

　　A. the greenhouse gas effect produced by human activities tends to have a much greater environmental effect than that of volcanic explosions

　　B. clouds of sulfur-rich gases tend to achieve greater heights in the stratosphere than do ash clouds

　　C. a particular explosion producing high sulfur and little ash had a greater environmental effect than the converse

　　D. the burning of fossil fuels tends to exacerbate the effects of sulfurous aerosols, but not those of ash clouds

　　20. The passage suggests that the effects of volcanic carbon dioxide on the environment differ from those of sulfurous gases in that

　　A. carbon dioxide tends to alleviate environmental haze, while sulfurous gases usually increase it

　　B. carbon dioxide tends to increase temperatures by trapping sunlight, while sulfurous gases tend to decrease temperatures by blocking it

　　C. sulfurous gases have played an even more significant role than carbon dioxide in pushing environmental temperatures outside the habitable range

　　D. sulfurous gases tend to decrease the level of solar radiation outside the earth’s atmosphere, while carbon dioxide plays only a negligible role

　　21. The author mentions the eruption of Mount St. Helens (lines 25-26) primarily in order to emphasize which of the following points?

　　A. The deep and enduring effect that volcanic eruptions have on the environment

　　B. The process by which classic volcanic eruptions tend to occur

　　C. The relative dearth of cases with scientists can judge the effects of volcanic eruptions

　　D. A sample case with which later volcanic explosions are compared

　　22. Which of the following best describes the organization the third paragraph of the passage?

　　A. A theory is proposed, considered, and amended.

　　B. Opposing views are presented, elaborated, and then reconciled.

　　C. A problem is described, then a solution is discussed and its effectiveness is affirmed.

　　D. A view is advanced, then refuted, and an alternative is suggested.

　　23. The passage suggests that which of the following would be true if volcanic eruptions did not take place?

　　A. Greenhouse effects on rising global temperatures would likely be somewhat less worrisome than those postulated by scientists today.

　　B. Acid rain by heavy industry would likely be more of a problem than it currently is, given the tendency of volcanic eruptions to hasten atmospheric cycles.

　　C. Global warming effects caused by human activities would be more substantial than they are today if volcanic cooling effects ceased to take place.

　　D. The environment would likely be cooler, for the atmosphere would contain fewer sulfurous gases and ash clouds.

　　24. Which of the following, if presented as the first sentence of a succeeding paragraph, would most logically continue the discussion presented in the passage?

　　A. The influence of volcanic eruptions on global weather patterns is almost completely understood at present.

　　B. Scientists have only begun to understand, however, the effects of these wavelengths of light on the global environment.

　　C. The human warming activities ameliorate by volcanic eruptions include those produced both by heavy industry and agriculture.

　　D. The reason that sulfate aerosols take an unusually large time to disperse owes primarily to meteorological factors, including the jet stream.

　　Passage 5

　　Much has been written about computer terminals and radiation effects, but sitting at the keyboard is now causing problems for many people. Carpal tunnel syndrome, resulting from a compressed nerve of the hand and wrist, affects tens of thousands of Americans each year. It has always been an occupational hazard for workers using drilling and cutting equipment. Now it is moving to officers, afflicting writers, programmers, data processors ---- anyone who spends long hours at a keyboard.

　　The syndrome occurs when tissues around the base of the wrist swell against the nerve, resulting in numbness and painful tingling in the hands, often happening at night. The condition can cause permanent loss of sensation and motor control.

　　The fault lies, in part, with poorly designed offices. Work stations that don’t allow employees to sit comfortably may put wrists, shoulders and arms under constant strain. The problem may be aggravated by the fact that people type faster and more continuously on computers, so that the hands and wrists rarely move into other positions. In some cases, surgery can solve the problem by decompressing the pinched nerve.

　　At the offices of the Los Angeles Times, where some of the reporters are afflicted, work stations are being redesigned, and exercise programs for shoulders, wrists and fingers are being developed, other recommended measurers for those trying to avoid the syndrome: hourly breaks and a five-hour-a-day typing limit.

　　25. “Radiation effects” in the first line probably refer to _____.

　　A. radio signals transmitted on the computer line

　　B. harmful effects of computer screens

　　C. the boredom of sitting before computers

　　D. the difficulties in learning to type

　　26. Which of the following is true according to the passage?

　　A. Workers using drilling and cutting equipment are using computers now.

　　B. A virus is spreading diseases among office workers, writers and programmers.

　　C. Computer users are threatened with sharper competition in getting employed.

　　D. Anyone who sits for long hours at a computer may develop a special condition.

　　27. In most serious cases of the problem, one may ______.

　　A. find his four limbs degenerating