油尘分离器串联在（）。
A.增压泵与扩散泵之间
B.机械泵与增压泵之间
C.扩散泵与机械泵之间
参考答案：C
There are fifty students, some are boys, ___________ are girls. [ ]
A. the other
B. the others
C. others
It's the fact _____ he doesn't know his own birthday surprises us all．
A．which, which
B．which, that
C．that, that
D．that, which
