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單項選擇題

Attempts are made to eliminate axial thrust in centrifugal pump by （）.

A.providing the impeller with balancing holes
B.the use of symmetrical impeller
C.neither A nor B
D.either A or B

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單項選擇題

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

單項選擇題

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)