Ответ:

1) 1. Nearer, the nearest

2. Larger, the largest

3. Thinner, the thinnest

4. Friendlier, the friendliest

5. Happier, the happiest

6. More beautiful, the most beautiful

7. Better, the best

8. Worse, the worst

9. Farther/further, the furthest/farthest

2) 1. The longest

2. Most famous

3. The best

4. The friendliest

5. the biggest

6. the funniest

3) 1. The cheetah is the fastest animal in the world

2. Russia is the largest country in the world

3. Salad is the healthiest food in this cafe

4. I am(I'm) the worst singer in my class

5. My brother is the best player in/on his team

4) 1. More

2. faster

3. the heaviest

4. the biggest

5. more

6. the highest