单项选择题
Deficient oxygen content inside a chain locker can be detected with（）.
A.litmus paper B.a combustible gas indicator C.an oxygen breathing apparatus D.an oxygen indicator
单项选择题 Continuous sounding of a fog whistle by a vessel is a signal（）.
单项选择题 Before entering the chain locker，you should（）.
单项选择题 According（）the report，the ship hit the wharf when berthing.
