The letter has been sent today. The book was written by Pushkin. The children returned from school. Who is singing in

1. The letter has been sent today. Present Perfect Passive Voice. Письмо отправлено сегодня. 2. The book was written by Pushkin. Past Simple Passive Voice. Книга была написана Пушкиным. 3. The children returned from school. Past Simple Active Voice. Дети вернулись из школы. 4. Who is singing in the next room? Present Continuous Active Voice. Кто поет в соседней комнате?