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  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  96
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.
As pointed out at the beginning of the passage, people used to think that air pollution______.
选项 A、caused widespread damage in the countryside
B、affected the entire eastern half of the United States
C、had damaging effects on health
D、existed merely in urban and industrial areas
答案D
解析 细节题。本题问的是：在文章开头提到的，人们过去认为空气污染______。根据首句“It was once thought that air pollution affected only the area immediately around large cities with factories and /or heavy automobiles traffic”可知曾经有这样一种看法，即空气污染只会影响那些工厂云集、交通密集的大城市附近地区。故选D。
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