Bài 2:
1. for
2. for
3. since
4. for
5. since
6. since
7. for
8. since
9. since
10. for
11. has been - since
12. has worked - for
13. has been - for
14. have sent - since
15. haven't eaten - for
16. have been - since
17. have lived - for
18. has gone - since
19. has lived - for
20. have attended - since
21. haven't seen - for
22. haven't had - for
23. has been - since