单选题 It was once thought that air pollution 'affected only the area immediately around large cities with factories or heavy automobile traffic. Today, we know 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 entire eastern halt' of the United States and led to health warning 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 in the air resulting from the burning of coal 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 ice cap will melt and cities such as New York, Boston, Miami, and New Orleans will be under water.
Another view, less widely held, is that increasing particulate 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 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.

单选题 According to the text, people used to think that air pollution______.

【正确答案】 D

【答案解析】由题干air pollution定位到第一句话It was once thought that air pollution affected only the area immediately around large cities with factories or heavy automobile traffic．过去人们认为空气污染只对工厂、交通密集型的大城市的周边地区有影响，因此选[D]。题干问的是used to think，而[A]、[B]陈述的是现在的事实，[C]是现在的认识，故排除。

单选题 Paragraph 1 implies that______.

【正确答案】 B

【答案解析】根据题干定位到第一段，第三句指出the increasing concentration of carbon dioxide in the air resulting from the burning of coal and oil is creating a“greenhouse effect”，燃烧煤、油等矿物燃料释放的二氧化碳越来越集中产生了温室效应，因此选[B]。煤、油本身并不是产生温室效应的原因，因此排除[A]；该句后半部分提到．...raising the world's average temperature，温室效应会使全球平均温度上升，但具体增加多少，文中并未提及，故排除[C]；第一段最后一句话提到the polar ice cap will melt and cities such as New York，Boston，Miami，and New Orleans will be under water，温室效应使得全球温度增高，由此引发的极地冰冠融化会淹没这些城市，并不是极地冰冠本身会淹没这些城市，故排除[D]。

单选题 It can be inferred from the text that______.

【正确答案】 C

【答案解析】第二段第二句话A drop of just a few degrees could create something close to new ice age and would make agriculture difficult of impossible in many of our top farming areas，可知气温下降将会产生新的冰川世纪，给农业带来毁灭性的灾难，因此选[C]。同样气温升高，极地冰冠融化，也会给全球带来巨大的灾难，因此排除[A]；未来全球温度可能升高，可能降低，但不会一下子发生剧烈变化，因此排除[B]；未来的气温不发生变化，保持稳定，只是人们做出的乐观预测，并不肯定，因此排除[D]。