Here are the correct answers for each blank in the exercise:

1. **hotter** - (A) hotter
2. **worse** - (C) worse
3. **bigger** - (B) bigger
4. **more beautiful** - (A) more beautiful
5. **better** - (D) better
6. **more graceful** - (A) more graceful
7. **boring** - (B) boring
8. **fluent** - (A) fluent
9. **fastest** - (C) fastest
10. **better** - (B) better
11. **as** - (D) as
12. **more hard-working** - (B) more hard-working
13. **more carefully** - (B) more carefully
14. **carefully** - (C) carefully
15. **well** - (D) well
16. **better** - (C) better
17. **easier** - (A) easier
18. **as** - (C) as
19. **more easy** - (C) more easy
20. **easier** - (D) easier

Please cross-check with the original text for any possible revisions or context.