单项选择题
A.for B.by C.at D.to
The self-contained breathing device should not be used ...
单项选择题The self-contained breathing device should not be used in which situation?（）
A.Oxygen deficient spaces B.Compartments containing poisonous vapors C.Fighting fires that produce heavy smoke D.Underwater search
The purpose of storm oil in a sea anchor is to（）.A.weig...
单项选择题The purpose of storm oil in a sea anchor is to（）.
A.weigh down the anchor B.lubricate the anchor C.repel dangerous fish D.smooth the sea
The process of waiting a period of time before pretensi...
单项选择题The process of waiting a period of time before pretensioning an anchor is known as（）.
A.soaking B.settling C.sinking D.bedding in
