Here are the suggested answers filled in with either the present perfect or past simple tense:

1. **have seen** (see) an ambulance recently. Maybe there’s an accident somewhere.
2. After he **arrived** (arrive) home, he **ate** (eat) dinner and **did** (do) the dishes.
3. A: What’s wrong with you?
4. B: I **lost** (lose) my bag! I cannot find it anywhere.
5. I **was** (be) in Tokyo for holiday for 3 weeks. I really enjoyed it.
6. We **did not meet** (not meet) Tommy last night.
7. When I **was** (be) 6 years old, I often **went** (go) fishing in the afternoon.
8. She **was** (be) a teacher before she **became** (become) a writer.
9. This is the second time I **have read** (read) Harry Potter.
10. A: When **did you arrive** (you/arrive)?
11. B: About 11 pm last night.
12. Jenny **arrived** (arrive)! Come and say hello!
13. Mozart **wrote** (write) more than 600 pieces of music.
14. She **came** (come) to Sydney in 2000.
15. How long **have you known** (know) Johnny? I know you see him often.
16. I **have never seen** (never/see) the sea before.
17. Dean **did not sleep** (not/sleep) last night. He’s still playing games.

Feel free to ask if you have any questions!