单项选择题
A.0.2Mpa B.0.4Mpa C.0.5Mpa D.0.6Mpa
A.1小时 B.2小时 C.半小时
A.O2≤0.5％ B.O2≤5％ C.O2≤0.2％
A.0.75~0.8Mpa，0.8~0.9Mpa B.0.6~0.85Mpa，0.7~0.75Mpa C.0.4~0.6Mpa，0.6~0.7Mpa
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