单项选择题
A.Top B.Lower C.Swing D.Adjust
When the derrick is stopped, the guy must be （）(收好).A.t...
单项选择题When the derrick is stopped, the guy must be （）(收好).
A.taken in B.slacked off C.adjusted D.stowed
When the derrick is topped, the guy must be （）(放松).A. s...
单项选择题When the derrick is topped, the guy must be （）(放松).
A. slacked off B. sent away C. sent out D. taken in
A （）(重吊杆)is used for lifting long heavy cargo.A. derric...
单项选择题A （）(重吊杆)is used for lifting long heavy cargo.
A. derrick B. crane C. jumbo boorn D. special crane
