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. Driven by economic profit, people neglect the damage on our environment caused by the "advanced civilization". Maybe the air pollution is the price the human beings have to pay for their development. But is it really worthwhile?
　　51. As pointed out at the beginning of the passage, people used to think that air pollution
　　A．caused widespread damage in the countryside
　　B．a(chǎn)ffected the entire eastern half of the United States
　　C．had damaged effect on health
　　D．existed merely in urban and industries areas
　　52. As to the greenhouse effect, the author
　　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 word soon
　　53. The word "offset" in the second paragraph could be replaced by
　　A．slip into
　　B 1 make up for
　　C．set up
　　D．catch up with
　　54. It can be concluded that
　　A．raising the world' s temperature only a few degrees would not do much harm to life on earth
　　B．lowering the world' s temperature merely a few degrees would lead many major farming areas to disaster
　　C．a(chǎn)lmost no temperature variations have occurred over the past decade
　　D．the world' s temperature will remain constant in the years to come
　　55. This passage is primarily about
　　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
　　參考譯文
　　曾經(jīng)有人認(rèn)為空氣污染只會影響到工廠林立、交通擁擠的大城市的周邊地區(qū)�，F(xiàn)在，人們意識到盡管這些地區(qū)空氣污染可能最嚴(yán)重，但實際上這個問題是全球性的。在過去的l0年里，發(fā)生過幾次這樣的現(xiàn)象，空氣污染產(chǎn)生的濃云籠罩在美國東部的上空，使人們警覺到郊區(qū)居民的健康也受到了威脅，盡管這里遠(yuǎn)離生產(chǎn)和交通的聚集地。事實上，整個地球的氣候都會受到空氣污染的影響。有些科學(xué)家認(rèn)為隨著化石燃料(煤和石油)的燃燒產(chǎn)生的二氧化碳在空氣中不斷聚集，“溫室效應(yīng)”正在產(chǎn)生——它會不斷儲存地球反射的熱量從而提高地球溫度。如果這一觀點(diǎn)正確，地球溫度哪怕只是升高幾度，大部分極地的冰帽就會融化，紐約、波士頓、邁阿密和新奧爾良等城市就會變成一片汪洋。
　　另外還有一個不被廣泛認(rèn)同的觀點(diǎn)是大氣中某些成分的增多會阻擋太陽光，導(dǎo)致地球溫度降低——這一結(jié)果也同樣是災(zāi)難性的。氣溫哪怕只是降低幾度也會造成一個類似的新的冰河時代，這會使農(nóng)業(yè)生產(chǎn)面臨困境，甚至許多高原農(nóng)業(yè)地區(qū)無法再進(jìn)行生產(chǎn)�，F(xiàn)在我們還無法確切地知道上述兩種情況哪一個會發(fā)生(盡管一個由專家完成的近期的政府報告表明溫室效應(yīng)非常有可能)。如果我們夠幸運(yùn)的話，也許這兩種傾向會互相抵消，地球溫度就可以保持不變了。，人們受金錢利益的驅(qū)動，忽略了“先進(jìn)文明”對環(huán)境帶來的侵害。也許空氣污染就是人類為發(fā)展所付出的代價。但這樣做真的值得嗎?