Ответ:
1. His book is more interesting than her book.
2. That is the funniest story in the book.
3. Jane is the most beautiful of five girls.
4. This river is longer than that river.
5. January is the most coldest month of the year.
6. She is taller than I.
7. This is the most happiest day in my life.
8. Nick is stronger than Rick.
9. She is the best student in her class.