关于超声探头，叙述正确的有（）。

A.发射超声波是超声换能器的逆压电效应

B.接收回声信号是换能器的压电效应

C.单层匹配层可提高宽频探头的信噪比

D.超声耦合剂可使探头与检查部位匹配良好

E.超声探头使用时要避免摔碰、折断导线

Why do we have to ____ Joan’s selfish behavior? She should learn to care for others．

A．be addicted to

B．be opposed of

C．get rid of

D．put up with