单项选择题 Which of the following pumps are self-priming, and can deal with liquid from a level below the pump: （） (1)reciprocating (2)vane (3)gear

单项选择题 Which of the following will be the advantage of a centrifugal pump as compared with a reciprocating pump?（） (1) Its discharge is continuous (2) It has no internal valves (3) Upon accidental closing of discharge valve, excessive pressure will not build up

单项选择题 The pipe friction and the resistance will （） as a result of an increase in the amount of fluid flowing through the system.