1. If I had known I would have told you.
2. They would have acted differently if they known what was wrong.
3. She would have agreed if you asked nicer.
4. The programme would have been less boring if you updated it to a more recent version such as 2.0.
5. If it hadn't so foggy we could see the ocean below us on the bridge.
6. If the chairman had noticed his atitude he woul have stopped.