单项选择题
To maintain design discharge pressure from a centrifugal pump, the design clearance must be maintained between the （）.
A.shaft and impeller B.motor and pump shaft C.casing and impeller wearing rings D.lantern ring and impeller
单项选择题 In a radial piston pump, reversal and control of fluid flow are accomplished by moving the （）.
单项选择题 Increasing the moisture content of conditioned air is known as （）.
单项选择题 A reciprocating air compressor is running roughly and vibrating excessively, indicating that the （）.
