题干
Each of the students in the playground when the bell rang.
A：has fun
B：have fun
C：was having fun
D：were having fun
答案(点此获取答案解析）
C
Each of the students in the playground when the bell rang.
A：has fun
B：have fun
C：was having fun
D：were having fun
N2↑+Cl2↑+4X↑+2O2↑，则X的化学式为( )