单项选择题
（）is main emergency fire system in all merchant ships.
A.CO2 system B.Foam system C.Dry power system D.Water supply system
单项选择题 Each fire drill shall not include（）.
单项选择题 Which instrument is used to measure the relative humidity of air?（）
单项选择题 （）is normally responsible for maintaining records of corrections to navigational charts and nautical publications.
