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°
单项选择题 Deck cranes require（） time to prepare for working cargo than derricks.
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 （）.
单项选择题 Most anchor handling equipment incorporates （） for mooring purposes.
