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單項(xiàng)選擇題

Among the basic categories of equipment, which of the following are used to convert the hydraulic energy into linear motion?（）

A.Hydraulic pumps
B.Valves
C.Hydraulic cylinders
D.Hydraulic motors

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單項(xiàng)選擇題

In a general cargo crane, （） is fitted to raise or lower the jib.

A.the slewing motor
B.the luffing motor
C.the hoisting motor
D.none of the above

單項(xiàng)選擇題

External and internal leakage in hydraulic systems may be caused by （）.

A.unusual vibration
B.excessive worn parts
C.abnormal pressure
D.any of the above

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