1. Keep silent or you'll wake the baby up

-> If you don't keep silent, you'll wake the baby up
2.  If you don't save electricity, you will pay a lot of money
4. She is very shy, that's why she doesn't enjoy parties.

=> If she shy, she may not enjoy parties.
5. he doesn't take any exerciese .he is so unhealthy.

=>if......he took exerciese .he would be healthy.......