Throughout history man has changed his physical environment in order to improve his way of life. With the tools of technolog

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问题     Throughout history man has changed his physical environment in order to improve his way of life.
    With the tools of technology he has altered many physical features of the earth. He has transformed woodlands into farmland, and made lakes and reservoirs out of rivers for irrigation purposes or hydroelectric power. Man has also modified the face of the earth by draining marshes and cutting through mountains to build roads and railways.
    However, man’s changes to the physical environment have not always had beneficial results. Today, pollution of the air and water is an increasing danger to the health of the planet. Each day thousands of tons of gases come out of the exhausts of motor vehicles; smoke from factories pollutes the air of industrialized areas and the surrounding areas of countryside. The air in cities is becoming increasingly unhealthy.
    The pollution of water is equally harmful. In the sea, pollution from oil is increasing and is killing enormous numbers of algae (水藻),fish and birds. The whole ecological balance of the sea is being changed. The same problem exists in rivers. Industrial wastes have already made many rivers lifeless.
    Conservationists believe that it is now necessary for man to limit the growth of technology in order to survive on earth.
The ecological balance of the sea is lost when______.

选项 A、people consume more fish than they used to
B、the ecological balance of the river is lost
C、large numbers of algae, fish and birds are killed
D、the production of marine petroleum is increased

答案C

解析 本题是一道具体细节题。问何时海洋的生态平衡就丧失了。利用查阅式阅读法,我们可以在文章第四段中找到相关信息。这段主要介绍了淡水污染给环境带来的危害。由于石油污染的增加,海中大量海藻、鱼和鸟死亡,海洋的生态平衡遭到破坏。同样的问题也存在于河流里,工业污水已使许多河流了无生机。因此,本题的正确答案应是C“当大量的海藻、鱼类和鸟类被杀死的时候”。A“人们比以前吃鱼吃得多了”,B“河流失去生态平衡”,D“海洋石油生产增加”,这三个选项都不是本题的正确答案。
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