单项选择题
A.50m B.75m C.100m D.120m
A.0.5~10m B.1~10m C.1~7m D.0.5~7m
A.0.3~1.0m,20m B.0.1~1.0m,20m C.0.3~1.0m,25m D.0.3~1.5m,15m
A.井道侧壁 B.井道底部 C.机房顶棚 D.井道上方机房顶棚
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