On the playground,we saw many boys    basketball.

A．playing

B．played

C．played the

D．stayed

活塞式压缩机的活塞杆的磨损大于（）mm的或表面有磨伤、划伤的，可考虑采取镀铬后磨外圆的方法修复。

A.0.30

B.0.25

C.0.20

D.0.15