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.
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 推理判断题。根据文章第一段最后两句,作者引用了一些科学家的观点,空气中二氧化碳的增多会导致温室效应。然后作者提出一种假设,如果这是真的的话,那么南极的冰雪就会融化,将纽约等城市淹没。然而对这种观点的正确性从文章很难看出。另外文中第二段第三句提到“今天我们还不能确定这两种情况能否发生…”,所以作者的态度应是“uncertain”。
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