单项选择题
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
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相关考题
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单项选择题
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 -
单项选择题
What type of valve is used to direct the flow of hydraulic fluid?（）
A.Relief valve
B.Direction control valve
C.Stop valve
D.Pressure control valve -
单项选择题
The rotor of the hydraulic motor rotates at a speed proportional to the （）.
A.flow of oil
B.pressure of oil
C.A and B
D.temperature of oil
