I didn’t know that you were in the hospital yesterday, so I didn’t visit you. → If I had known that you were in the hospital yesterday, I would have visited you.

Hurry up or you will be late for school. → If you don't hurry up, you will be late for school.

My mother is very busy, so she can’t help me now. → If my mother were not very busy, she could help me now.

Lan didn’t call me because she didn’t know my phone number. → If Lan had known my phone number, she would have called me.

You’re unhealthy because you don’t take exercise. → If you took exercise, you would be healthy.

He didn't study his lessons very carefully, so he gets bad marks now. → If he had studied his lessons very carefully, he wouldn't get bad marks now.

Leon often causes accidents because he drives carelessly. → If Leon didn't drive carelessly, he wouldn't often cause accidents.

I can’t apply for that job because I don’t know English. → If I knew English, I could apply for that job.

Lien is overweight because she eats too much chocolate. → If Lien didn't eat too much chocolate, she wouldn't be overweight.

His father often punishes him for his laziness. → If he were not lazy, his father wouldn't often punish him.