问题
单项选择题
主要通风机必须配备同等能力的备用通风机，在主要通风机因故停止运转时，必须在（）分钟内启动备用通风机。
A.5
B.10
C.15
D.20
答案
参考答案：B
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主要通风机必须配备同等能力的备用通风机，在主要通风机因故停止运转时，必须在（）分钟内启动备用通风机。
A.5
B.10
C.15
D.20
参考答案：B
Passage Three
Why do most of us hear women voices more clearly
A．Because their voices are more pleasant to listen to.
B．Because the possessing of voices in the brain is different.
C．Because listening to women requires more brain activities.
D．Because women’s voices are full of melodies.