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單項選擇題

Which of the following pumps will build up a bursting pressure or stall their motors if the discharge valves are closed?（）
(1) gear
(2) centrifugal
(3) screw

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

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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

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

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