单项选择题
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （） (1) reciprocating (2) vane (3) gear
A.（1）only B.（1）and（2） C.（1），（2）and（3） D.（2）and（3）
Which of the following pumps are self-priming, and can ...
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （） (1) reciprocating (2) rotary (3) centrifugal
A positive displacement pump is that where the volume o...
单项选择题A positive displacement pump is that where the volume of the pump chamber is alternately （） to draw the liquid in and then （） to force the liquid out.
A.increased；decreased B.decreased；increased C.decreased；decreased D.increased；increased
The pressure head of a water pump is given in the unit ...
单项选择题The pressure head of a water pump is given in the unit of （）.
A.kg B.MPa C.mH20 D.None of the above
