Передайте следующие предложения в passive voice. 1.They published the series of books last year. 2.They coloured the walls in green and yellow stripes. 3.They discussed the topic two days ago. 4.The author introduced his main characters only in the 2nd part of the story. 5.Librarians help people to find a book on any subject. 6.The invention of printing changed a lot in history. 7.People wrote books by hand in ancient times. 8.Thematic selections of books develop their visitors' reading preferences.