=>
16. B wrote
17. A QKTD when QKĐ
18. A QKĐ
19. B last night at this time -> QKTD
20. D After QKHT, QKĐ
31. A -> walked
32. A -> had eaten
33. A -> were you doing
34. D -> had already left
35. A -> knew
36. A -> disappeared
37. D -> cooked
38. C -> have seen

39. B -> had graduated
40. B -> has been
41. B thì HTHT
42. D for + khoảng time
43. D It's time since QKĐ
44. C thì HTHT
45. A for + khoảng time

1. were watching/failed
2. has changed/came
3. have spent/got
4. has
5. comes
6. was
7. were you doing/rang
8. haven't seen
9. will come
10. worked
11. discovered
12. are singing
13. Have you received 
14. have Bob and Mary been
15. has asked
16. was watching
17. had done/went
18. is coming
19. haven't talked
20. felt/was doing

16.b ; 17.A ; 18A, 19B, 20D;

31A was walking(đáp án này là ghi trên mạng nh theo mk câu D cx sai vì phải là  playing
Cấu trúc see sb do sth(hoặc saw sb did sth) là thấy hết toàn bộ sự việc,

còn see sb doing sth(hoặc saw sb  doing sth) là chỉ nhìn thấy 1 phần sự việc. Đây là suy đoán của mk th bn thấy sai thì nhớ nói nhé. :(

32 A: had eaten

33A were you doing.;

34 D had already left

35 C since

36A disappeared;

37D cooked ;

38C have seen;

39.B had graduated;

40  B has been vì cho đến h k có phụ nữ dc lm T.thống(qua từ Up to now)

41.B ; 42 D; 43C(?) ; 44C;45A

Phần Word form 1.was watching/ failed 

2. has changed/ came

3.has spent/ got

4. has

5. come

6. was

7.were doing/ rang

8. haven't seen

9.will come

10.was working

11. discovered 

12. are singing

13. have received

14. have been

15. has asked

16. was watching

17. had done/ went

18. is coming

19. haven't talked

20. felt/ was doing(cho mk hỏi là đề có sai k vì chỉ có là fall asleep( ngủ) chứ để feel thì mk k bt chia như thế nào 
chỉ có là feel sleepy(cảm thấy buồn ngủ)