Bài a:
1. younger => youngest
2. busyer => busier
3. that => than
4. China => chinese
5. have => has
Bài b:
1. His house is to the right of the bookstore.
2. It's a tall building.
3. Tom travels to work by car every morning.
4. ko rõ lắm nên chưa làm đc
9. weren't
10. was
11. where were you
12. Did they help
13. hasn't play
14. called
15. moved
16. have been
17. went
18. spent
19. heard
20. have you finished
21. will go
22. goes
23. will visit
24. collected
25. have you ever done
26. goes
27. go
28. seeing
29. to play
30. has learned
31. watched
32. arranging
33. working
34. swimming
35. eating
36. living
37. watching
38. built
39. organized
40. visited
41. will you be