下列气体与空气混合后，遇明火时可能发生爆炸的是 [ ]
A．氧气
B．甲烷
C．氮气
D．二氧化碳
答案：B
At last, Lucy made the baby _____ and the baby began to laugh.[ ]
A. stop crying
B. to stop crying
C. stop to say
计算并填写下表。
