Change the sentences into the passive voice

1. We should clean these windows before tomorrow.
2. The workers gave the boss some flowers.
3. The police followed the thieves into a building.
4. The mechanic can’t fix my car.
5. The neighbour has told us the news.
6. The students painted the walls last year.
7. The old woman feeds the pigeons every day.
8. They will pick up John at this office.
9. She showed the visitors the new house.
10. You shouldn’t throw litter on the ground.
11. The teacher asked the students a very difficult question at the oral exam.
12. First, we have to read the text and then, we have to do the exercises.
13. His parents promised Tom a hundred Euros if he passed the test.
14. Did they repair all the windows?
15. The news surprised us all.
16. Is the teacher correcting the exams right now?
17. Someone has sent John a mysterious letter.
18. Where did they find the book?
19. The taxi driver drove us to the airport.
20. Many people have seen a UFO in this area.
21. Have they watered the plants?
22. Someone stole my purse while I was doing the shopping.
23. The secretary has already sent all the documents to Mr. Smith.
24. They have offered Michael an excellent job in a British company.
25. The police could arrest the bank robbers when they were crossing the border.
26. Someone has used the computer without permission.
27. My grandmother is baking a delicious cake.
28. The maid was cleaning my hotel room when I came in.