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问题 问答题

有一只电影录音用电容传声器，灵敏度为10mV/Pa，用dB表示为多少？

答案

参考答案：

20lgs/so==-40dB(以1V/Pa为0dB)

10mV/Pa用分贝表示为-40dB。

问答题

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单项选择题

You are looking at two assets, A and B. The expected return on A is 15%, and the expected return on B is 17% , while the standard deviation of A is 20%, and the standard deviation of B is 18%. The two are correlated at 45%. What is the standard deviation of a portfolio made up of 40% A and the rest in B

A．

A. 2.6%.

B．

B. 19.0%.

C．

C. 16.2%.
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