A.12% B.14% C.16% D.18%
A.成煤過程和煤的變質(zhì)程度 B.圍巖性質(zhì) C.地質(zhì)構(gòu)造 D.風量變化
A.膠皮風筒 B.帆布風筒 C.玻璃鋼風筒 D.帶剛性骨架可伸縮風筒