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问题 单项选择题

外侧滑转弯是由于离心力比升力的水平分量还大，把飞机向转弯的外侧拉。下列说法错误的是（）

A.外侧滑转弯可以通过增加倾斜角修正

B.为维持一个给定的角速度，倾斜角必须随离心力变化

C.在高速飞机上对侧滑进行修正非常重要

答案

参考答案：B

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.

16（）

A.effected 

B.affected 

C.damaged 

D.killed
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单项选择题

地面上不同地区的热量差异会引起空气流动。下列示意图中符合热力环流原理的是（）

A.A

B.B

C.C

D.D
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