单项选择题
There is no power for the （）(起货机).
A.winch B.crane C.derrick D.boom
单项选择题 Containers are loaded and discharged by （）(龙门吊).
单项选择题 Our heavy derrick has been （）(不用)for a long time.
单项选择题 （）(调高) the derrick, please.
