离心泵严重抽空,会引起压力表(),泵()。
参考答案:回零;打不上量
When and where to build the new factory ____yet.
A.is not decided
B.are not decided
C.has not decided
D.have not decided
抽油机井偏心井口装臵的()偏臵于油管挂一侧。
A、生产管柱
B、防喷闸门
C、观察
D、抽油杆