单项选择题
Removing which will extinguish a fire?（）.
A.Nitrogen B.Carbon dioxide C.Sodium D.Oxygen
单项选择题 Regular foam can be used on all but which flammable liquid?（）
单项选择题 Recharging a previously used cartridge-operated dry-chemical extinguisher is accomplished by（）.
单项选择题 Radiation spreads a fire by（）.
