在特殊疑问句和一般疑问句中 如果出现did，那就是倒装句。
特殊疑问句例子:
What did you do yesterday?
Did you finish homework yet?
When did he come back from school?
其他情况例子:
Only then did a girl come out of the room.
Not only did I pass the exam, but I got high marks.
