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單項(xiàng)選擇題

Which pump is the self-priming pump?（）

A.turbine
B.centrifugal
C.ejector
D.mixed flow

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單項(xiàng)選擇題

The younger motorman as well as the others （） to operate the oil separator.

A.has learnt
B.have learnt
C.learn
D.are learning

單項(xiàng)選擇題

A water pump can not supply water after startingIt may be caused by （）.

A.closed discharge valve
B.broken pipe line
C.worn shaft
D.both A and B

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