. What a pity. Considering his ability and experience, he _________ better.

A．need have done

B．must have done

C．can have done

D．might have done

JIM型计量泵的传动部分可将电动机的旋转运动转变成（）的往复运动。

A、蜗杆

B、连杆

C、曲轴

D、柱塞