单项选择题
The pump discharge pressure will be considerably higher than the pressure at the （）.
A.pump entry branch B.outlet pipe C.impeller D.None of the above is true
单项选择题 What is the purpose of a relief valve?（）
单项选择题 A （） pump is that where the volume of the pump chamber is alternately increased to draw the liquid in and then decreased to force the liquid out.
单项选择题 A reciprocating pump belongs to （） according to its working principle.
