1. I didn’t knowu that you were in hospital, so I didn’t visit you.
If I had konwn tha you were in hospital, I would have visited you.
2. Hurry up or you will be late.
If you don't hunrry up, you will be late.
3. She is very busy, so she can’t help me now.
If she weren 't very busy, she could help my now.
4. He didn’t phone me because he didn’t know my phone number.
If he had konwn my phone number, he would have phoned me
.5. You’re unfit because you don’t take exercise.
If you took (move) exercise, you would be fit/ wouldn't be unfit.
6. Unless you are careful, you will cut yourself with that knife.
If you are not , you'll cut with that knife.
7. If I have time, I’ll help you
Unless. I have time, I won't help you....
8. He didn’t study his lessons very carefully, so he gets bad marks now.
If he had studied his lessons very carefully, he woudn't get bad marks now.
9. Dick often causes accidents because he drives carelessly.
If dick drove carefully, he wouldn't cause acciddent (often).
10. I can’t apply for that job because I don’t know English.
If I knew English, I could apply for that jop.