$Đáp^{}$ $án^{}:$

1, Expensive, cheaper, cheapest

2, quiet, noisier, noisiest

3, boring, more fantastic, most fantastic

4, fun, more boring, most boring

5, inconvenient, more___, most_____

6, Unhistoric, more___, most_____

7, Unnarrow, more___, most_____

8, Peaceless, more___, most_____

9, Inexciting, more___, most_____

10, Unterrible, more___, most_____'

11, Unpolluted, more___, most_____

12, Short, longer, longest

13, Short, higher, highest

14, Big, smaller, smallest

15, Cold, hotter, hottest

16, Dry, wetter, wettest

17, unfriendly, friendlier, friendliest

18, Tall, shorter, shortest

19, bad, better, best

20, good, worse, worst