Here are the best options for each sentence in the exercise:

21. John and Ann **B. got** married last Saturday.
22. We **A. will become** successful people later.
23. When I entered the room, everyone **B. was dancing**.
24. How long **C. have you been** able to drive? Since 1990.
25. Jane and I **D. finished** school in 1987.
26. While Tom **A. was playing** tennis, Ann **B. took** a shower.
27. His brother **B. finished** high school 6 years ago.
28. We have lived here **C. since** 1990.
29. Now, my sister **A. is having** a bicycle of her own.
30. Don't bother me while I **B. was working**.
31. How long **A. have you been / left** school?
32. I have waited for you **A. since early morning**.
33. I saw Jack yesterday morning while I **A. walked**.
34. My brother **A. doesn’t usually go** out at weekend.
35. Everyday, my sister **D. usually cleans** the floor.
36. They **A. have/is ringing** the doorbell.
37. He **B. left** for London one year ago.
38. This is the second time they **A. have left** that club.

Feel free to ask if you need further assistance!