单项选择题
A.Not B.Notto C.Don’t D.Can
Before leaving the harbour, all derricks must be （）prop...
单项选择题Before leaving the harbour, all derricks must be （）properly.
A.tightened B.secured C.unfastened D.loaded
（）operation, any obstacles in the way of hatches must b...
单项选择题（）operation, any obstacles in the way of hatches must be removed and cleaned.
A.Before B.During C.After D.Within
Each （）consists of two or more panels.A.coverB.hatchC.d...
单项选择题Each （）consists of two or more panels.
A.cover B.hatch C.derrick D.winch
