A.氧; B.可燃氣; C.氧和可燃氣; D.氮
A.氧含量≥18.5%; B.可燃氣含量<0.5%; C.可燃氣含量<0.2%,氧含量≥18.5%; D.可燃氣含量<0.2%
A.18.5% B.0.5% C.0.2% D.0%