I) 

30. C    ( Đã làm gì trước đó - S + have/has + V3/Ed + before)

31. B ( if 2)

32. D (htht + since , qkđ + when)

33. D ( Sau verb + adv)

34. B ( noun or noun)

35. C ( Favorite - yêu thích)

36. D ( looking forward to + V-ing)

37. A ( let s.o do sth)

38. B ( polluted air - không khí ô nhiễm)

39. D ( try hard - cố gắng )

40. B ( used to + V-inf - đã từng )

41. B (if 2)

42. C ( S + have/has + V3/Ed for + tg - Đã bao lâu kể từ khi )

43. B ( be fond of + V-ing)

44. D ( Sau verb + adv)

45. B ( Câu tường thuật = lùi thì )

46. B ( stop + V-ing. - ngưng làm gì)

47. B ( be + adj)

48. C ( turn off - tắt đèn)

49. A (correspond - trao đổi thư từ)

50. B ( trước noun dùng adj )

II)

1. How about going ....   ( How about + V-ing)

2. We will have .... ( Xảy ra ở tương lai dấu hiệu - next weekend-)

3.She would like to go ... ( Would like + to-v)

4. Let me .... ( Let s.o do sth)

5. Bell started experimenting ( started + V-ing)

6. This test is easier than that one ( so sánh hơn tính từ ngắn thêm er)

7. Everybody in my neighborhood is ... ( Everybody số ít)

8. We have learnt to play the piano since 2005 ( mốc tg dùng since)

9. I used to work .... ( Used to + V-inf)

10. We have the same idea as your dad in the disscussion ( have the same idea as s.o)

III)

1.D.  2.B  3.C 4.D 5.B

1. C, I've been

2. B, There weren't so many people.

3. D, since

4. D, perfectly

5. B, or

6. C, favorite

7. D, forward

8. A, go

9. B, polluted

10. A, Hardly tried

11. B, used to

12. A, were

13. C, has learned

14. B, wearing

14. D, beautifully

15. B, came

16. B, making

17. B, careful

18. B, off

19. A, correspond

20. B, beautiful

II

1. Go => going

2. Weekend => week

3. Going => to go

4. Let's => let

5. experimented =>experimenting

6. Are => is

7. For => since

8. Working => work ( used to + v bare)

9. With => as

III

1. D

2. A

3. C

4. D

5. B