2011年1月8日，美元对人民币的汇率是661.480元；1月16日，美元对人民币的汇率变为657.380元。此时，美元的汇率（　 ）

A．没有变化

B．升高了

C．下降了

D．不好判断

Have you ever heard your own voice "Of course," you say.
Has anyone else ever heard your voice Again you say, "Of course. "
But that’ s not quite true. Nobody else has ever heard your voice—the way you hear it. When you talk, you set up sound waves. The air outside your head carries the sound waves to your outer ears. But, of course, the sound of your voice begins inside your head. The bones of your head pick up the sound waves, too. They carry the sound waves straight to your inner ears. You get the sound from the outside and the inside too. Other people get just the sound waves from the outside. That’s why they don’t hear your voice the way you do.

The phrase "pick up" here means ______.

A．to raise

B．to get

C．to choose

D．to pull