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單項選擇題

A centrifugal impeller consists of a number of vanes curving （） from the direction of rotation.

A.backwards
B.forwards
C.upward
D.downwards

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單項選擇題

When installed for bilge pumping or ballast duty, centrifugal pumps require a （） to remove air from the suction pipe.

A.air chamber
B.head lank
C.primer
D.prime mover

單項選擇題

Water enters the rotating impeller through the entry, known as “（）”, at the centre.

A.eye
B.hole
C.balance holes
D.opening

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