代用
参考答案：
不用本来指称某人或某事物的名词，而用另一个与之相关的词语代替。
大尺度天气系统
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
