问题

The little child usually felt frightened at night, so not until ___________.
A:did he fall asleep his mother left the room
B:he fell asleep had his mother left the room
C:did he fall asleep did his mother leave the room
D:he fell asleep did his mother leave the room
B:he fell asleep had his mother left the room
C:did he fall asleep did his mother leave the room
D:he fell asleep did his mother leave the room
正确答案是: