---Are you ____ of the dark?  ---Yes, so I always go to sleep with my bedroom lights ____ .

A．worried, off

B．afraid, on

C．fond, turn on

D．frightened, off

压扩器的作用是将话音信号的（）进行压缩扩张，达到改善话音通路信杂比的目的。

A.频率范围

B.动态范围

C.响度范围

D.清晰度