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單項選擇題

The pressure head of a water pump is given in the unit of （）.

A.kg
B.MPa
C.mH20
D.None of the above

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單項選擇題

Which of the following are components of a mechanical seal? （）
(1) stationary ring
(2) rotational ring
(3) packing
(4)spring

A.(1), (2) and (3)
B.(1), (2) and (4)
C.(2), (3) and (4)
D.None of the above

單項選擇題

The gear, screw, and vane pumps are all classified as （）.

A.variable stroke pumps
B.multistage pumps
C.positive displacement pumps
D.triple-ported pumps

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