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

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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.
This passage is primarily concerned with______.
选项 A、the greenhouse effect
B、the bunting of fossil fuels
C、the potential effect of air pollution
D、the likelihood of a new ice age
答案C
解析 主旨题。本题问的是：这篇文章是主要关于______。需要综合全文内容，进行归纳和推理。本文论述了可能发生的温室效应和新冰河时代均为空气污染造成的潜在后果。故选C。
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大学英语四级

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