单项选择题
A.立即停钻 B.加速钻进 C.减速钻进 D.时快时慢钻进
A.0.7% B.0.8% C.1% D.1.5%
A.回风侧上方0.5m范围内 B.回风侧下方0.5m范围内 C.进风侧上方0.5m范围内 D.进风侧下方0.5m范围内