人体通过的电流值与通电时间的乘积，对人身的安全是一个界限，通

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问题单项选择题

人体通过的电流值与通电时间的乘积，对人身的安全是一个界限，通常认为（）mA为安全值。

A.10

B.20

C.30

D.40

答案

参考答案：C

选择题

I don't know____ makes her afraid of having her business discussed. [ ]

A. what it is about Mary that

B. that is it about Mary that

C. what is it about Mary that

D. that it is about Mary that

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