单项选择题

硫黄回收单元停产冷却时,吹扫气合格的标准是()

A.H2S< 10ppm,SO2< 10ppm,O2>19.5%
B.H2S< 10ppm,SO2< 10ppm,CH4< 20ppm
C.H2S< 10ppm,S< 10ppm,O2>19.5%
D.H2S< 10ppm,SO2< 10ppm,O2< 19.5%