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问题 填空题

游标卡尺的零位误差是以游标零刻线和尾刻线与主尺相应刻线的（）来表示。检定时，移动尺框使两测量面接触，分别在尺框（）和（）两种情况下观察。

答案

参考答案：重合度；紧固；松开

单项选择题

歌剧产生于16世纪末的意大利，综合了音乐、戏剧、诗歌、舞蹈、美术等艺术形式，以唱歌为主的戏剧形式。下列选项中哪一项不是歌剧（）。

A.（奥）莫扎特《费加罗的婚礼》

B.（俄）柴可夫斯基《胡桃夹子》

C.（法）比才《卡门》

D.（意）普契尼《图兰朵》
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单项选择题

It is clear that some chemicals can damage the health of animals and humans. (1) , this is not the only problem that (2) be caused by the careless use of chemicals. Chemicals can also (3) the ecological balance of the environment. If the ecological balance is disturbed, the results can be (4) serious.

The (5) of DDT illustrates the problem. DDT, a chemical which kills insects, at first seemed to be a perfect answer (6) many problems. It would control insects that caused dangerous diseases, (7) insects that caused billions of dollars of damage to crops every year. Governments permitted and even (8) the use of DDT. Farmers in many countries (9) to spray it on their crops. The (10) results were good: Damage to crops (11) down, and profits went up. However, the chemical had effects which the scientists didn’t see in (12) . First, it also killed insects which were the (13) enemies of the harmful insects and which were therefore beneficial to farmers. Second, and perhaps worse, DDT did not kill (14) harmful insect. A few insects had natural resistance to the chemical. They (15) and reproduced in large numbers. In a few years there were large numbers of insects which were not (16) by DDT, and there were (17) insects which could act as natural (18) on these new "super-insects". Finally, it became clear that DDT was not solving the insect problem. In fact, it was making the problem worse. It (19) became necessary to find a second (20) for the effects of the first.

13（）

A.natural 

B.ill 

C.ugly 

D.friendly
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