1. 单句改错

1. （1） These who have plenty of money will help their friends.
   
3. （2） This is the longest train which I have ever seen.
   
5. （3） Which we all know, swimming is a very good sport.
   
7. （4） The radio set which I bought it last week has gone wrong.
   
9. （5） He paid the boy $10 for washing ten windows, most of them hadn't been cleaned for at least a year.