1.When I arrived,the teacher was writing on the black board

2.When they were walking down the stairs,they heard a strange noise

3.When I last saw them,they were trying to find a new flat near the office

4.I was walking along the street when I suddenly felt something hit me in the back

1. When I arrived,the teacher was writing on the black boar                                                       

2. When they were walking down the stairs,they heard a strange noise

3.  When I last saw them,they were trying to find a new flat near the office

4.  I was walking along the street when I suddenly felt something hit me in the back

5sao nha bạn