A. Study this example situation:
Last month Gary was in hospital for an operation. Liz didn't know this, so she didn't
go to visit him. They met a few days ago.
Liz said: If I had known you were in hospital, I would have gone to visit you.
Liz said: If I had known you were in hospital... . The real situation was that she didn't
know he was in hospital.
When you are talking about the past, you use if + had ('d) ... (if I had known/been/done etc.):