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單項(xiàng)選擇題

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

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單項(xiàng)選擇題

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

A.(1)only
B.(1)and(2)
C.(1),(2)and(3)
D.(2)and(3)

單項(xiàng)選擇題

In （） pumps a closed discharge valve will cause bursting discharge pressure.

A.centrifugal
B.plunger
C.injector
D.water