Давайте преобразуем предложенные вами предложения в пассивный залог.
Использование пассивного залога
Когда мы меняем предложение в активном залоге на пассивный, основное внимание уделяется действию и его результату, а не деятелю (т.е. тому, кто выполняет действие). Пассивный залог образуется с помощью глагола "to be" и причастия прошедшего времени основного глагола.
Преобразование предложений в пассивный залог
A policeman is using the telephone.
→ The telephone is being used (by a policeman).Architects design buildings.
→ Buildings are designed (by architects).A group of small boys are feeding the monkeys.
→ The monkeys are being fed (by a group of small boys).Bees make honey.
→ Honey is made (by bees).Prisoners are building the new road.
→ The new road is being built (by prisoners).She should take her passport.
→ Her passport should be taken (by her).You must return all these books to the library.
→ All these books must be returned to the library (by you).
Теперь переформулируем следующие предложения так, чтобы не указывать агента:
We use this room only when we have guests.
→ This room is only used when guests are present.Someone switched off the light and closed the window.
→ The light was switched off, and the window was closed.They are building a new hotel.
→ A new hotel is being built.Someone will serve coffee.
→ Coffee will be served.People mustn't leave cars in front of the building.
→ Cars mustn't be left in front of the building.The postman delivered the mail in the afternoon.
→ The mail was delivered in the afternoon.Somebody told him to come to the office by five o'clock.
→ He was told to come to the office by five o'clock.A thief stole my wallet and returned it only when I promised a reward.
→ My wallet was stolen and returned only when a reward was promised.
Заключение
Теперь вы видите, как преобразовать активные предложения в пассивные, при этом сосредотачиваясь на действии, а не на том, кто его совершает. Понимание этой структуры поможет вам лучше использовать пассивный залог в английском языке.