下列零件中属于活塞压缩机工作机构的有（）。
A.机身
B.气阀
C.气缸
D.活塞
E.曲轴
参考答案：B, C, D
Minister Bill De Blasio in office fewer than 48 hours when he came face to face with his biggest challenge in his life．
A．has been
B．had been
C．would be
D．is
润滑油库应保持干净，做到（）进行维护。
A.定员
B.定点
C.定时
D.定点、定员、定时
