17. They are being watched to work by the teacher. 18. Peter hasn't been seen since the day of the party. 19. The suspects were being followed by the police. 20. An apple is thought to be good for you. 21. All the school have to be improved in the city. 22. A new bridge is going to be built. 23. Two department stores have been built this year. 24. Tree are being planted in the schoolyard by the students at the moment. 25. Their car was being washed when I came. 26. The floor is being cleaned now. 27. Our homework has just been finished. 28. This problem can't be solved. 29. Jean's are sold all over the world. 30. A new skirt was given to me by my mother. I was given skirt by my mother.