单项选择题
A.the slewing motor
B.the luffing motor
C.the hoisting motor
D.none of the above
单项选择题 The crane is usually mounted on a pedestal to offer adequate （） to the operator.
单项选择题 In a ordinary cargo crane, （） is fitted to rotate the crane.
单项选择题 The single acting cylinder is the simplest form where pressure is applied to the full area of the piston head to move the load through piston rod extensionThe load causes rod （） when the drive pressure is released.