A group of students are writing a song.
The song is being written by a group of students.
They have built a new hospital near the airport.
A new hospital has been built near the airport.
They are building a new ring-road round the city.
A new ring-road is being built round the city.
I didn't realise that somebody was recording our conversation.
I didn't realise our conversation was being recorded.
When we got to the stadium, we learnt that they had cancelled the game.
When we got to the stadium, we learnt that the game had been cancelled.
Somebody cleaned the room.
The room was cleaned.
Somebody is using the computer at the moment.
The computer is being used at the moment.
They have postponed the meeting.
The meeting has been postponed.