单项选择题
The amount of fluid delivered by a gear 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 true
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) ejector (2) screw (3) centrifugal
单项选择题 In （） pumps a closed discharge valve will cause bursting discharge pressure.
单项选择题 The volute pump is one in which the impeller （）.
