离心水泵在填料箱或水管法兰处进气,都会导致水泵抽不上水。
参考答案:对
Tom is in the _______. He is playing ping-pong,[ ]
A. classroom
B. gym
C. library
They had an accident on the road and didn’t ________ at their hotel until after midnight.
A.check out
B.check in
C.check on
D.check over