Put the following sentences into the passive voice.
1. My grandfather built this house.
2. Carol always waters the flowers.
3. The boys did the homework.
4. Susan wrote this email.
5. George has opened a hotel.
6. Peter solved this problem.
7. An electric fault caused the fire.
8. Her mother will clean the room.
9. The police arrested three men.
10. We haven't seen her since weeks.
11. They will pull down the old building.
12. Helen found the key.
