单项选择题
As a sailor on duty you must know how to （）(调整)derricks.
A. taken in B. slack off C. adjust D. send out
单项选择题 There are many （）(类型)of ship’s cargo handling equipment.
单项选择题 When the derrick changes its （）(角度), its lifting capacity changes correspondingly.
单项选择题 The derrick can’t be （）(超载).
