使物料在定子和转子间受剪切、被粉碎的设备是（）

A．球磨机

B．冲击式粉碎机

C．滚压式粉碎机

D．胶体磨

E．气流式粉碎机

In the swimming race, three boats will be ____in case of an emergency.

A．standing by

B．turning on

C．getting on

D．running on