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  3. Acid rain is a very serious air and water pollution problem. Many people feel-that it is the most serious pollution problem that

Acid rain is a very serious air and water pollution problem. Many people feel-that it is the most serious pollution problem that

admin2013-06-02  69
问题     Acid rain is a very serious air and water pollution problem. Many people feel-that it is the most serious pollution problem that we now face. Scientists say that plant and animal life in thousands of lakes in the United States and Canada has already been destroyed by acid rain.
    Acid rain forms in the upper atmosphere. There, sulfur dioxide and nitrogen oxides mix with water vapor. They mix with water vapor to form sulfuric acid and nitric acid. When the vapor condenses and rain falls, the acids fall with it. Every time acid rain falls in a lake, the level of acid in the lake rises. Over time, it can rise to the point at which plants and insects cannot survive. Without plants, which supply oxygen, and insects, which supply food, fish die. The lake becomes a dead lake.
    The problem of acid rain has greatly increased in the last few years. Most of the blame for acid rain has been placed on industries. However, some people feel that ineffective air pollution laws are also to blame for the acid rain problem.
    A few years ago, many cities and states passed local air pollution laws. The laws were written to impr9ve the air quality in the cities and states. However, the laws usually didn’t say anything about the amount of pollution that an industry could pump into the air. Industries found a way to meet the new pollution laws without reducing the amount of pollution they released.  They met the new standards by building taller smokestacks.
    With the taller smokestacks, air pollutants were released higher up into the atmosphere. The wind carried them far away from the polluting factory. To the people near the factory, the air seemed cleaner. However, the pollution that they once got was now coming down hundreds of miles away in the form of acid rain.
Which of the following is TRUE about acid rain?
选项 A、It is acknowledged by scientists to be the most serious pollution problem that human beings now face.
B、Many endangered species are on the verge of extinction because of acid rain.
C、Acid rain is composed of sulfur dioxide and nitrogen oxides mixed with water vapor found in the upper atmosphere.
D、Acid rain is mostly found in the United States and Canada.
答案C
解析 A是错误的。酸雨是目前人类面临的最严重的环境污染问题只是一些人的看法，不是科学家的共识。B这项说一些濒危物种的生存受到酸雨的威胁，这在文章中没有提到。酸雨是由大气层上层的二氧化硫、氧化氮和水混合生成的。
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