present perfect or past simple

16. When did you leave the office yesterday?  - I left at about 8.30. yesterday.
17. Was the weather cold yesterday? - Yes, it was.
18. She stopped smoking two years ago.
19. They went to Germany when he was only 4.
20. Have you ever found any money in the street?
21. Who invented the telephone?
22. James hasn't finished his homework yet.
23. I have already cleaned the flat.
24. Where were the children last weekend? - They were at the museum.
25. Yesterday I saw a big blue Ford parking in front of our house.
26. Karol hasn't been to this house since she was a child.
27. The lecture has just begun. You are late.
28. He broke his leg in a skiing accident last winter.
29. He doesn't know my husband. He has never met him.
30. I haven't bought a warm coat yet.