單項選擇題The usual number of single-acting pistons used in a variable stroke axial-piston pump is （）.

A.3 or 5
B.5 or 7
C.7 or 9
D.9 or 11


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1.單項選擇題The heat identified by only a change in temperature is known as （）.

A.sensible heat
B.latent heat
C.total heat
D.residual heat

2.單項選擇題The static suction lift of a pump is the difference in elevation between the （）.

A.centerline of the pump and the level of the liquid in the suction well when the source of liquid is below the pump
B.centerline of the pump and the suction liquid level when the source of liquid is above the pump
C.centerline of the pump and the level of the discharge liquid
D.liquid levels of the suction and discharge

3.單項選擇題The sum of the sensible heat and the latent heat of any substance is known as （）.

A.total heat
B.residual heat
C.specific heat
D.superheat

4.單項選擇題With respect to centrifugal pump impellers, which of the following descriptions represents the correct centrifugal pump classification? （）

A.Single stage or multistage
B.High pressure or low pressure
C.Open or close coupled
D.Horizontal or vertical

5.單項選擇題If a radial piston hydraulic pump fails to deliver rated fluid volume, the cause can be （）.

A.contaminated fluid
B.pitted thrust rings
C.worn pintle bearings
D.obstructed suctions passage