单句改错7个1 April 1st is a day which strange things may happen.2

单句改错7个
1 April 1st is a day which strange things may happen.2 I'll never forget the day in which I went to college.3 The number of the workers in his factory are about 3,000.4 When he was young he was put in the prison many times.5 Today we have reached a stage which we are preparing for the marriage.6 Nobody believes the reason why hw gave us.7 He has two sons,one of them works as a teacher.