3. If he could park near his office, he would have come by car.
4. If my house hadn't been guarded by two big dogs, it would have been broken into last night.
5. If the flat had been clearly numbered, it wouldn't have been difficult to find anyone.
6. If my brother had left the car keys, I could have picked him up at the station.
7. If you had prepared the lesson carefully, you wouldn't have got bad marks