There was one thought that air pollution affected only the area immediately around large cities with factories and heavy automob

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问题     There was one thought that air pollution affected only the area immediately around large cities with factories and heavy automobile traffic.At present, we realize that although these are the areas with the worst air pollution, the problem is literally worldwide. (76) On several occasions over the past decade, a heavy cloud of air pollution has covered the east of the United States and brought health warnings in rural areas away from any major concentration of manufacturing and automobile traffic.In fact, the very climate of the entire earth may be infected by air pollution. Some scientists consider that the increasing concentration of carbon dioxide in the air resulting from the burning of fossil fuels (coal and oil) is creating a "greenhouse effect"--conserving 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 ice cap will melt and cities such as New York, Boston, Miami, and New Orleans will be in water.
(77) 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. Today we do not know for sure that either of these conditions will happen (though one recent government report drafted by exports in the field concluded that the greenhouse effect is very possible). Perhaps, if we are lucky enough, 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 about _________.

选项 A、the greenhouse effect
B、the burning of fossil fuels
C、the potential effect of air pollution
D、the likelihood of a new ice age

答案C

解析 归纳概括题。文章第一段提到地球的气温可能受到空气污染的影响,接下来谈到两种因空气污染可能造成的后果,所以应选C“空气污染可能带来的影响”。其他三个选项都只是文章主题的一个方面。
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