Sure, let's fill in the blanks with the correct verb forms:

1. I **haven't heard** from him since he **disappeared** two years ago.
2. After the guests **had left**, she **went** back into the living-room and **turned** off the light.
3. By the time you finished cooking they **had done** their homework.
4. This time yesterday they **were sitting** in the train on their way to Paris.
5. I came late to class. When I **entered** the teacher **was writing** something on the blackboard.
6. She **got** into her shoes, **put** on her coat and **went** to the door.
7. David **was** born after his father **had died**.
8. When I **was** a child, I **wanted** to be a doctor.
9. At 4 p.m. yesterday? Well, I **was working** in my office at that time.
10. The audience **listened** to everything he said last night.
11. Yesterday thieves **broke** into the house and **stole** a lot of fur coats while the guests **were dancing**.
12. He **had done** his homework before he went to the cinema.
13. What **did you do** after you **went** home yesterday?
14. Tom **won't come** here tomorrow.
15. John **was watching** TV at 8 last evening.
16. Dick **had started** school before he **was** seven.
17. What **were you doing** when I **rang** you last night?
18. John **has driven** that car ever since I **have known** him.
19. Columbus **discovered** America more than 400 years ago.
20. When the teacher came in, the pupils **were playing** games.

These answers should be correct based on the context provided.