單項(xiàng)選擇題A deepwell pump is a type of（）.

A.screw pump
B.centrifugal pump
C.eductor
D.gear pump


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1.單項(xiàng)選擇題A definite advantage of using water as a fire extiguishing agent is its characteristic of（）.

A.alternate expansion and contraction as water in a liquid state becomes a vapor
B.absorption of smoke and gases as water is converted from a liquid to a vapor
C.rapid contraction as water is converted from a liquid to a vapor
D.rapid expansion as water absorbs heat and changes to steam

2.單項(xiàng)選擇題A design modification of an anchor chain which prevents kinking is the（）.

A.detachable link
B.stud link
C.Kenter link
D.connection link

3.單項(xiàng)選擇題A device fitted over the discharge opening on a relief valve consisting of one or two woven wire fabrics is called a（）.

A.flame stopper
B.flame screen
C.flame filter
D.flame restrictor

5.單項(xiàng)選擇題A Doppler log in the bottom return mode indicates the（）.

A.velocity of the current
B.bottom characteristics
C.depth of the water
D.speed over the ground