III.

1. is bigger

2. are more expensive

3. is warmer

4. is faster

5. is more difficult

6. is more cheerful 

IV.
1.  Huy is fatter than his brother
2. The city is quier than the country
3. A mountain is higher than a hill
4. This novel is worse than that novel
5. The blue chair is more comfortable than the red one
VI.
1. slow ->slower
2. heavyer ->heavier
5. interestinger -> more interesting

Study well!

@hahoang207

Iv,
1,  Huy is fatter than his brother
2. The city is quier than the country
3. A mountain is higher than a hill
4. This novel is worse than that novel
5. The blue chair is more comfortable than the red one
VI.
1. slow->slower
2. heavyer->heavier
5.. interestinger -> more interesting