声波的频率范围是(  )。

声波的频率范围是(  )。A.20~200Hz B.20~2000Hz C.20~20 000Hz D.20~200 000Hz

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一平面简谐横波的波动表达式为y=0.05Cos(20πt+47πχ)(SI)。取k=0,±l,±2,…,则t=0.5s时

一平面简谐横波的波动表达式为y=0.05Cos(20πt+47πχ)(SI)。取k=0,±l,±2,…,则t=0.5s时各波峰所在处的位置为(  )。

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What's the main reason the man doesn't like watching plays?

What's the main reason the man doesn't like watching plays?A.Because they areexp

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I didn' t feel like __________ , so he suggested __________a

I didn' t feel like __________ , so he suggested __________a taxi,A.to walk; tak

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