1. In the picture galleries and museums you meet well-mannered and
well-dressed people. Well-mannered and well-dressed people are met in the
picture galleries and museums.
2. Heating systems and cars mainly pollute air. Air is mainly polluted by
heating systems and cars
3. Somebody is cleaning the room at the moment. The room is being cleaned at
the moment.
4. They have built a new hospital near the park .A new hospital has been
built near the park by them
5. I think I’ll close the window. I think the
window will be closed by me