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【单选题】

第(9)空应选择()

A.wanted
B.began
C.decided
D.arranged

A.
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 erous 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 the problem worse. It (19) became necessary to find a second (20) for the effects of the first.
B.
 
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【单选题】在选择价值分析对象时,不能作为重点分析对象的是( )。

A.
成本低的工程和构配件
B.
使用费用较高的工程和构配件
C.
体积与重量大的工程和构件
D.
结构复杂的工程和构配件

【单选题】利率互换中固定利率一般选择()的利率。

A.
双方协商而定
B.
使互换初始价值为0
C.
选取的参照利率的即期
D.
使互换初始价值最大

【单选题】粗基准选择原则不正确的是()。

A.
选择不加工的表面
B.
选择加工余量均匀表面
C.
选择余量和公差最小的表面
D.
粗基准一经选定可使用多次