Sally        her MP4 for 3 years.

A．have bought

B．has bought

C．have had

D．has had

内、外钳工操作时，要密切配合，互相注意安全，以避免（）。

A.碰坏钳头

B.碰坏钻具

C.伤及对方

D.碰伤套管