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
单项选择题 Lifeboat launching is operated at intervals of （）months.
单项选择题 Fire drill is carried out once a （）.
单项选择题 Any emergency pump situated （）machinery space should also be started.
