单项选择题
Halon extinguishes fire primarily by（）.
A.cooling B.smothering C.shielding of radiant heat D.breaking the chain reaction
单项选择题 Halon extinguishes a fire by（）.
单项选择题 Halon extinguishers used on a class C fire should be directed at the（）.
单项选择题 Good housekeeping on a vessel prevents fires by（）.
