单项选择题
The safe working load of the derrick is （）.
A.5 tons B.5 metres C.5 feet D.5 years
单项选择题 It’s going to rain. Don’t forget （）the hatches.
单项选择题 The crane is （）. Could you ask somebody to repair it?
单项选择题 The sailor on duty is （）the derrick now.
