2. 外语
  3. It was once thought that air pollution affected only the area immediately around large cities with factories and/or heavy autom

It was once thought that air pollution affected only the area immediately around large cities with factories and/or heavy autom

admin2010-05-26  31
问题     It was once thought that air pollution affected only the area immediately around large cities with factories  and/or heavy automobiles(汽车)traffic. Today, we know that although these are the areas with the worst air pollution, the problem is literally(简直地 )worldwide. On several occasions over file past decade, a heavy cloud of air pollution has covered the entire eastern half of the United States and led to health warnings even in rural areas away from any major concentration of manufacturing and automobile traffic. In fact, the very climate of the entire earth may be affected by air pollution. Some scientists feel that the increasing concentration of carbon dioxide(二氧化碳)in the air resulting from the burning of fossil(化石)fuels (com and oil) is creating a "greenhouse effect"—holding in heat reflected from the earth and raising the world’s average temperature. If this view is correct and the world’s temperature is raised only a few degrees, much of the polar(极地的) ice cap will much and cities such as New York, Boston, Miami, and New Orleans will be under water.
    Another view, less widely held, is that increasing particular matter in the atmosphere is blocking sunlight and lowering the earth’s temperature--a result that would be equally disastrous. A drop of just a few degrees could create something close to a new ice age, and would make agriculture difficult or impossible in many of our top fanning areas. At present we do not know for sure that either of these conditions will happen (though one recent government report prepared by experts in the field concluded that the greenhouse effect is very likely). Perhaps, if we are very lucky, the two tendencies will offset each other and the world’s temperature will stay about the same as it is now.
The word "offset" in the second paragraph could best be replaced by______.
选项 A、slip into
B、make up for
C、set up
D、catch up with
答案B
解析 词汇题。本题问的是：第二段中的“offset’’可由——来代替。文章第1段是关于温室效应带来的地球温度升高，第2段是关于新冰河时代带来的地球温度降低。由文章最后一句“If we are very lucky，the two tendencies will offset each other and the world’s temperature will stay about the same as it is now”可知地球温度能够保持不变的前提是这一升一降的趋势互相抵消，make up for有补偿、弥补的意思，故选B。
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