4.met

5.thanked

6.was

7.am 

8.was

9.has driven,knew

10.have speak

11.were you doing,rang

12.have seen

13.haven't seen

14.left,knew

15.was playing,arrived

16.will come,see

17.came,are you ready

18.will come

19.will you spend

20.blooms

21.haven't lived

22.have never forgeted,just told me

23.are preparing

24.has worked

25.was working

26.build,fly

27.have lost ,can

28.has smoked

29.arrived,just went

30.are Bod and Mary

31.have you received

32.was joining,was

33.was writing

34.left,haven't heard

35.Did you spoken,haven't seen ,couldn't,saw

36.discovered

37.did your father die,was knowing,died

38.haven't seen

39.were waiting

40.heard

41.do you study

42.haven't received,left

43.am having

44.am speaking

45.is coming

46.is

47.don't eat

48.have lived

49.is cutting

50.did the house build

51.is singing

Đáp án.

1. was

2. taught - has graduated

3. doesn't watch

4. met

5. thanked

6. was

7. am

8. had been

9. has driven - known

10. Speak

11. were you doing - rang

12. had never seen

13. haven't seen

14. will leave - knows

15. was playing - arrived

16. will come - see

17. will come - Are you ready 

18. will come

19. will you spend

20. bloom

21. haven't lived

22. will never forget - have just told

23. are preparing

24. has worked

25. worked

26. build - fly

27. have lose - Can

28. hasn't smoked

29. arrived - has just gone

30.been

31. have you received

32. joined - was

33. wrote

34.left - haven't heard