单项选择题
In cargo crane, （） for lifting the load.
A.a hoisting motor B.a luffing motor C.a mooring motor D.a slewing motor
单项选择题 Manually operated band brakes may be fitted and （） will have a brake arranged to fail-safe.
单项选择题 The （） is used for hauling in or letting out the wires or ropes.
单项选择题 （） may be fitted for operating the derrick topping lift (the wire which adjusts the derrick height).
