1 一般疑问句：Were you a student two years ago?Yes,I was.No,I wasn't.
否定句：I wasn't a student two years ago.
提问：1 What did you do two years ago?
2 When were you a student?
2 Did he play basketball last Sunday?Yes,he did.No,he didn't.
He didn't play basketball last Sunday.
What did he do last Sunday?
When did he play basketball?
3 Were there any books on the table yesterday?Yes,there were.No,there weren't.
There weren't any books on the table yesterday.
How many books were there on the table yesterday?