单项选择题
A.独立通风 B.串联通风 C.矿井通风 D.矿井反风
A.14% B.15% C.16% D.17%
A.45g/m3 B.55g/m3 C.65g/m3 D.75g/m3
A.0.5% B.1% C.1.5% D.2%
微信扫一扫,加关注免费搜题