2. 外语
  3. There are hidden factors which scientists call " feedback mechanisms ". No one knows quite how they will 【C1】______ with the cha

There are hidden factors which scientists call " feedback mechanisms ". No one knows quite how they will 【C1】______ with the cha

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问题     There are hidden factors which scientists call " feedback mechanisms ". No one knows quite how they will 【C1】______ with the changing climate. Here’s one example: plants and animals, 【C2】______ to climate change over centuries.【C3】______ the current estimate of half a degree centigrade of warming per decade, vegetation may not keep 【C4】______. Climatologist James Hansen predicts climate zones will shift toward the poles【C5】______50 to 75 kilometers a year—faster than trees can naturally migrate. Species that【C6】______ themselves in an unfamiliar environment will die. The 1,000-kilometre wide strip of forest running【C7】______Canada, the USSR and Scandinavia could be cut 【C8】______. Millions of dying trees would soon lead to massive forest fires, 【C9】______ tons of CO2 and further boosting global warming.
    There are dozens of other possible "feedback mechanisms". Higher temperatures will【C10】______ condensation and increase cloudiness, which may actually【C11】______ down global warming. Others, like the "albedo" effect, will do the【C12】______. The "albedo" effect is the amount of solar energy reflected by the earth’s surface. As the northern ice and snow【C13】______and the darker sea and land pokes through, more heat will be absorbed,【C14】______ the temperature increase.
    Even if we【C15】______ to magically stop all greenhouse-gas【C16】______ tomorrow the impact on global climate would continue for decades.【C17】______ will simply make the problem worse. In the developed world prosperity has been 【C18】______on 150 years of cheap fossil fuels. Material progress has been linked 【C19】______ energy consumption. Today 75 percent of all the world’s energy is consumed by a quarter of the world’s population. The average rich world 【C20】______adds about 3. 2 tons of CO2 yearly to the atmosphere, more than four times the level added by each Third World citizen.
【C4】
选项 A、off
B、down
C、on
D、up
答案D
解析 固定搭配题。四个选项均能与keep搭配，但意义不同：keep off“让开，不接近”；keep down“卧倒，镇压，控制，缩减”；keep on“继续，穿着……不脱”；keep up“保持，跟上”。根据原文意思，[D]为答案。
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