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问题 单项选择题

抗生素属于微生物的（）

A.营养物质

B.次级代谢产物

C.初级代谢产物

D.结构单元

答案

参考答案：B

选择题
It was reported that an agreement ____ between the two companies and that they would carry out a project together.

A. reached
B. had been reached
C. was reached
D. had reached
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单项选择题

信访事项应当自行政机关受理之日起60日内办结；情况复杂的，经本行政机关负责人批准，可以适当延长办理期限，但延长期限不得超过( )日，并告知信访人延期理由。

A．10

B．15

C．20

D．30
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