A.50mm B.60mm C.70mm D.80mm
A.瓦斯突出 B.煤炭自燃 C.顶板冒落
A.1/3 B.2/3 C.1/4 D.1/5
A.100 B.150 C.200 D.120
A.1列车长度处 B.10m C.15m D.12m
