单项选择题
A fire of escaping liquefied flammable gas is best extinguished by（）.
A.cooling the gas below the ignition point B.cutting off the supply of oxygen C.stopping the flow of gas D.interrupting the chain reaction
单项选择题 A chemical additive to LPG gives it a characteristic（）.
单项选择题 On a hydrocarbon flammability chart the line which extends from 0% to 21.8% oxygen，lying tangent to the flammability range，is called the（）.
