Put the following sentences into the Passive Voice:
1. We heat the house by gas. 2. They are pulling down a lot of old houses in this street. 3. People may keep books from the library for a fortnight. After that they must return them. 4. Someone has already told him about this tour. 5. Everyone expected him to pass his exams well. 6. They have lengthened the runway in this airport. 7. We shall throw out the mushrooms if they are poisonous. 8. One cannot do it so quickly. 9. Nobody had warned me