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问题 填空题
若约定：a是不为1的有理数，我们把
1
1-a
称为a的差倒数．如：2的差倒数是
1
1-2
=-1，-1的差倒数是
1
1-(-1)
=
1
2
．已知a1=-
1
3
，a2是a1的差倒数，a3是a2的差倒数，a4是a3的差倒数，…，依此类推，则a6=______，a2010=______．
答案

a1=-

1
3
，

a2=

1
1-(-
1
3
)
=
3
4
，

a3=

1
1-
3
4
=4，

a4=

1
1-4
=-
1
3
，

∴3个数一循环，

∴a6应该是循环的最后1个数，a2010是循环的第3个数．

∴a6=4，a2010=4．

故答案为4，4．

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.

第（8）空应选择（）

A．asked

B．requested

C．declared

D．encouraged
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单项选择题

中药新药证书证号的格式是（）

A.国药准字H+4位年号+4位顺序号

B.国药准字S+4位年号+4位顺序号

C.国药证字Z+4位年号+4位顺序号

D.国药证字H+4位年号+4位顺序号
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