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.
【C15】
选项 A、shall
B、are
C、will
D、were
答案D
解析 虚拟语气题。由于原句所述情形不可能发生，所以使用的是虚拟语气，[D]were是答案。
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