1. since four o'clock

2. 10 years ago

3. since Sunday

4. for six weeks 

5. for three years

6. eight months ago ( đề sai ở trên my sister, phần rewrite lại là he)

7. for three weeks

8. for an hour

9. since

10. for

11. since

12. since

13. since

14. for

15. since

16. for

17. since

18. for

19. since

20. for

21. since

1.since four o'clock

2.ten years ago

3.since Sunday

4.for six weeks 

5.for three years

6.eight months ago (Sai đề chỗ my sister hoạc he)

7.for three weeks

8.for an hour

9.since

10.for

11.since

12.since

13.since

14.for

15.since

16.for

17.since

18.for

19.since

20.for

21. since.