单项选择题
A. release a lifebuoy B. release a life-jacket C. release a lifeboat D. release a life-raft
发警报（）A. sound alarmB. make alarmC. send alarmD. receive...
单项选择题发警报（）
A. sound alarm B. make alarm C. send alarm D. receive alarm
每月一次（）A. once a monthB. once a weekC. once a dayD. once...
单项选择题每月一次（）
A. once a month B. once a week C. once a day D. once a year
封闭舱室（）A.enclose roomB. enclosed spaceC. closed spaceD. ...
单项选择题封闭舱室（）
A.enclose room B. enclosed space C. closed space D. closed room
