A.露天B.敞口C.隔絕空氣D.通風(fēng)
A.無(wú)煙煤、煙煤、褐煤B.無(wú)煙煤、褐煤、煙煤C.褐煤、煙煤、無(wú)煙煤D.煙煤、無(wú)煙煤、褐煤
A.絲炭B.褐煤C.暗煤D.泥炭