As she was doing her homework,the little girl-------(fall) asleep.怎么填?

As she was doing her homework,the little girl-------(fall) asleep.怎么填?
As she was doing her homework,the little girl-------(fall) asleep.怎么填?

As she was doing her homework,the little girl-------(fall) asleep.怎么填?
fell 短暂性动词,不能用进行

was falling