Ответ:

1. the most experienced

2. best

3. the most interesting

4. the most brilliant

5. the most pleasant

6. the cleanest

7. the greatest

8. the most difficult

9. the most hardworking

10. the most open-minded

11. the eldest

12. largest

13. most kind-hearted

14. the stupidest

15. the most changeable

16. the most comfortable

17. the most creditable

18. the most popular

19. the ugliest

20. worst