6. It's the first time that I have met such a famous person.

7. They haven't visited me since 5 years ago.

8. The last time I was to Bristol was 3 years ago.

9. Laurence last saw his sister was when she left for Japan.

10. The last time Lucy wore that dress was Barbara's wedding.

11. My sister began to study French 2 years ago.

12. It's such a mess that I have never seen in my life.

14. It's 4 years that Robert and Catherine have been married.

15. It's the dirtiest-looking dog that I have ever seen.

16. It's hours and hours ago that Mary rang.

17. Tom has been ill since 3 days ago.

18. She has left university 2 years ago.

19. This is the first time that I have tasted such a delicious cake.

20. When did you last see Mary?