题目内容

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. 1()

A. Therefore
B. However
C. Meanwhile
D. Besides

查看答案
更多问题

在本节中,你将听到10个对话,每个对话有一个问题。请从[A]、[B]、[C]三个选项中选出答案,并标在试卷的相应位置;每段话后有20秒钟的停顿,以便回答问题和阅读下一个问题。每段对话读两遍。

A. Black.
Brown.
C. Blond.

在本节中,你将听到10个简短话语,请从[A]、[B]、[C]三个选项中选出一个最佳应答,并标在试卷的相应位置,每个话语后有20秒钟的停顿,以便选择答案和阅读下一个问题。每个话语读两遍。

A. The same to you.
B. Happy birthday.
C. Thank you very much.

在本节中,你将听到10个简短话语,请从[A]、[B]、[C]三个选项中选出一个最佳应答,并标在试卷的相应位置,每个话语后有20秒钟的停顿,以便选择答案和阅读下一个问题。每个话语读两遍。

A. What about going to tile zoo
B. Sounds good.
C. That’s a good idea.

In 1933, it was the first time for the Empire State Building to appear in a film in "King Kong".

答案查题题库