启动离心泵前要盘泵（），查看转动是否正常。
A.l圈
B.1.5圈
C.2~3圈
D.5圈
参考答案：C
蒸汽质量不合格有什么危害？
---Excuse me, could you tell me the way to the airport?
---_____.
A．You can't miss it.
B．Why do you ask me?
C．No, I don't know.
D．I'm sorry, I'm also new here.
