1. I can't send her a postcard because I don't know her address
=> If
2. Ann has a bad cold, so she can't go to the circus today
=> If
3. They don't clean the window that's why the room looks rather dark
=>If
4. Sue was ill, so she couldn't go to the party
=> If
5. They didn't have enough money therefore, they didn't buy the bigger house
=> If
6. Mary was not injured in the crash because she was wearing a seat belt => If
7. The bus didn't stop because you didn't put your hand up
=> If
