【单选题】【消耗次数：1】
胰岛素有两条链，其分子结构的最高层次是().
①
A.一级结构
②
B.二级结构
③
C.三级结构
④
D.四级结构
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综合管理类公务员职级序列分为：一级巡视员、二级巡视员、一级调研员、二级调研员、三级调研员、四级调研员、一级主任科员、二级主任科员、三级主任科员、四级主任科员、一级科员、二级科员、三级科员。
①
Y
②
N
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三级的结构构件，结构重要性系数γ0应分别取为（）。
①
一级1.3，二级1.2，三级1.1
②
一级1.2，二级1.1，三级1.0
③
一级1.1，二级1.0，三级0.9
④
一级1.0，二级0.9，三级0.8
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根据所操作生物因子的危害程度和采取的防护措施，将实验室生物安全防护水平分为一级、二级、三级和四级，防护水平最高的是（ ）
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Television is a remarkable_________ !
①
discussion
②
suggestion
③
invention
④
declaration
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You can buy things_________ special low prices when department stores have sales.
①
at
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in
③
on
④
for
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阅读理解：阅读下列短文，回答文后问题，选择最佳答案Trees mainly serve man in three important ways: They provide him with wood and other products; they provide him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important．In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil allowing the rain to sink in and also bind(固定) the soil, thus preventing it from being washed away easily；but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When the top-soil is gone, nothing remains but worthless desert.Two thousand years ago，a rich and powerful country cut down its trees to build warships, with which to gain itself an empire．It set up the empire, but, without its trees, its soil became poor and grew weak. When the empire fell to pieces, the home country found itself faced by floods and starvation(饥荒)．2. In many places forests slowly disappear because __________.
①
A. many trees have been cut down by man
②
B. new trees are not well looked after
③
C. man has not paid enough attention to planting trees
④
D. all the above
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①
put forward
②
put up
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put away
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put on
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Why has jogging become so popular? Because jogging is a very_________ exercise.
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boring
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disturbing
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frustrating
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interesting
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Your long-term memory_________ everythingthat you remember.
①
concludes
②
conveys
③
closes
④
contains