A.1/5 B.1/4 C.1/3 D.1/2
A.無煙煤 B.焦煤 C.肥煤 D.貧煤
A.貧煤、瘦煤、焦煤、肥煤 B.褐煤、長焰煤、氣煤、肥煤 C.氣煤、無煙煤、肥煤、焦煤 D.焦煤、肥煤、不粘煤、無煙煤