单项选择题
A.Two derricks B.A derrick and a crane C.Two cranes D.A crane and a winch
Some cranes are mounted in pairs on a common platform w...
单项选择题Some cranes are mounted in pairs on a common platform which can be rotated through（）.
A.360° B.270° C.180° D.90°
Deck cranes require（） time to prepare for working cargo...
单项选择题Deck cranes require（） time to prepare for working cargo than derricks.
A.less B.more C.many D.much
The duty of a deck winch is to lift and lower a load by...
单项选择题The duty of a deck winch is to lift and lower a load by means of a fixed rope on （）.
A.a warp end B.a mooring winch C.a worm gear D.a barrel
