单项选择题
The amount of fluid delivered by a centrifugal pump can be regulated by （）.
A.throttling the pressure line B.changing the speed of the rotor C.either A or B D.None of the above is tree
单项选择题 While flowing through the volute in a centrifugal pump, part of the （） energy of the liquid is converted to （） energy.
单项选择题 The amount of fluid delivered by a screw pump can be regulated by （）.
单项选择题 A screw pump belongs to （） according to its working principle.
