单项选择题
An oxygen indicator can be used to determine if there is（）.
A.sufficient oxygen in a compartment to support life B.combustible gases present C.hydrogen gases present D.All of the above
单项选择题 Anchoring and fishing in this area are（）.
单项选择题 Any ship damping a pipe could（）an immedidate danger of fire.
单项选择题 As a vessel sinks to a depth of 15 feet, the hydrostatic trip releases the life raft container from its cradle by（）.
