英语句子改错Gary drove at seventymiles before the police stopped h

1.Gary drove at seventy miles an hour before the police stopped him.
2.The twins want to know whether they are in the same class.
3.The boy who is running likes fishing very much.
4.I understand what you meant yesterday.
5.He didn't tell me where he stayed those days.
6.What were you doing when the fire started?
7.I found that the mirror was broken by someone.
8.I don't know if they are having a meeting in Room 301 now.