单项选择题
A.injection valve B.relief valve C.discharge valve D.inlet filter
In （） pump a closed discharge valve will not cause exce...
单项选择题In （） pump a closed discharge valve will not cause excessive pressure to build up.
A.gear B.vane C.screw D.centrifugal
Centrifugal pumps are non-positive and a fairly （） unit...
单项选择题Centrifugal pumps are non-positive and a fairly （） unit.
A.low pressure B.low discharge C.low speed D.high pressure
Gear pumps are （） type because they discharge a near co...
单项选择题Gear pumps are （） type because they discharge a near constant amount of liquid regardless of pressure.
A.positive displacement B.non-positive displacement C.mixed-flow D.axial-flow
