單項選擇題When the union purchase derrick is operated, one derrick is positioned over the quayside and the other almost vertically over the ().

A.dock
B.hold
C.pedestal
D.machinery space


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1.單項選擇題In a general cargo crane, () is fitted to lift the cargo load.

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

3.單項選擇題In a ordinary cargo crane, () is fitted to rotate the crane.

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