The boy often _________basketball after school. But now he _________piano.

A．plays; is playing the

B．play the; plays

C．is playing the; is playing

D．plays the; is playing

探伤面上涂敷耦合剂的主要目的是（）

A、防止探头磨损

B、消除探头与探测面之间的空气

C、有利于探头滑动

D、防止工件生锈