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问题 单项选择题

银燕展翅，巨轮远航……两岸“三通”，化茧成蝶，回首前尘，两岸“咫尺天涯，重重阻碍”；展望未来，两岸“天涯咫尺，处处机遇”。两岸关系的发展历程表明（）

①矛盾双方在一定条件下可以相互转化

②物质的运动是相对的，静止是绝对的

③事物的发展是前进性和曲折性的统一

④人们可以根据自己的意愿建立新的具体联系

A.①②④

B.②③④

C.①③

D.②④

答案

参考答案：C

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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单项选择题

下列关于单倍体、二倍体、多倍体叙述，不正确的是：（）

A.由受精卵发育成的生物体细胞中，有几个染色体组就叫做几倍体

B.由配子发育成的生物体细胞中，有几个染色体组都叫做单倍体

C.单倍体一般高度不孕，多倍体一般茎杆粗壮，果实种子较大

D.单倍体都是纯种，多倍体的等位基因至少三个
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