单项选择题
A hydrostatic release mechanism for a liferaft（）.
A.must be wet before it will release B.should be kept in a watertight except in an emergency C.will inflate the raft in its cradle if operaterd manually D.must be submerged to a certain depth to release automatically
单项选择题 A hygrometer is a device used for determining（）.
单项选择题 A large oil fire on the deck of a ship can be fought most effectively with（）.
单项选择题 A life line must be conncted to the life raft（）.
