A which of the verb tenses in the sentences below is used to describe:
a) an action that happened before another past action?
b) an action in progress (going on) around a particular past moment?
c) a completed action connected with the present?
d) a single past action?

1. I've just had a snack and I shall enjoy a peach.
2. She ate the caviar and she ate the salmon.
3. It was twenty years ago and I was living in Paris.
4. Foyot's was far beyond my means that I had never even thought of going there.