单项选择题
A.water B.oil C.fire D.A+B
CO2 and Halon extinguishers are used for electrical fir...
单项选择题CO2 and Halon extinguishers are used for electrical fire, as well as （）fire.
A.common B.oil C.electrical D.chemical
Lifeboat launching is operated at intervals of （）months...
单项选择题Lifeboat launching is operated at intervals of （）months.
A.one B.two C.three D.four
Fire drill is carried out once a （）.A.yearB.dayC.weekD....
单项选择题Fire drill is carried out once a （）.
A.year B.day C.week D.month
