单项选择题
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
单项选择题 The sum of the sensible heat and the latent heat of any substance is known as （）.
单项选择题 With respect to centrifugal pump impellers, which of the following descriptions represents the correct centrifugal pump classification? （）
单项选择题 If a radial piston hydraulic pump fails to deliver rated fluid volume, the cause can be （）.