无码高清视频|成人自拍视频|欧美成人午夜无码A片秀色直播|草美女视频网站|美女被操网站在线观看

單項選擇題

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

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

你可能感興趣的試題

單項選擇題

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

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

單項選擇題

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

A.reduce
B.rise
C.raise
D.fall