单项选择题
A.the toping light B.the board brake C.the fail-safe D.the barrel shaft
For occasional heavy loads, two cranes can be arranged ...
单项选择题For occasional heavy loads, two cranes can be arranged to work together. The operating （） for deck crane motors may be hydraulic electric.
A.principle B.medium C.instruction D.voltage
In a general cargo crane, three principal movements are...
单项选择题In a general cargo crane, three principal movements are （）； （）； （）.
A.hoisting；luffing；slewing B.lifting；raising；lowering C.rotating；raising；handling D.hosting；lowering；moving
A warp end may be fitted for operating the derrick topp...
单项选择题A warp end may be fitted for operating the derrick topping wire which adjusts the derrick （）.
A.length B.slack C.height D.rotation direction
