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. 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.
   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 farming areas. Today we do not know for sure that either of these conditions will happen (though one recent government report drafted by experts 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.
As to the greenhouse effect, the author

选项 A、shares the same view with the scientists
B、is uncertain of its occurrence
C、rejects it as being ungrounded
D、thinks that it will destroy the world soon

答案B

解析 细节题。文章第一段第五句和第二段第一句分别陈述了两种观点,根据第二段第三句可知,现在我们也无法确定会发生哪种情况,选项B(不确定会不会发生)正确。选项A(与科学家观点一致)和选项D(认为温室效应很快会摧毁世界)文章中并未提及。选项C(因为不切实际而反对)与文章不符,文中作者并未表现出反对的态度。故本题选B。
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