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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  56
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.
Why do lakes in the United States and Canada become dead lakes?
选项 A、Fish in the lakes die because acid rain deprives them of oxygen.
B、Fish in the lakes die from taking in poisonous substances released from the acids.
C、Fish in the lakes die from direct contact with accumulated acid in the water.
D、Air pollutants are dissolved in the water and thus kill the fish.
答案A
解析 文章第二段说明，因为酸雨破坏了水中的氧气，湖里的鱼无法生存。
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