A.水管接頭脫落或水管破B.水管堵塞C.管路水源被切斷
A.碳粒子B.CaF2C.CaO
A.先開(kāi)氧氣,再開(kāi)煤氣B.先開(kāi)煤氣,再開(kāi)氧氣C.氧氣、煤氣同時(shí)打開(kāi)