3.1. If he buys the ticket he . . . . . . (to be) able to fly tomorrow.
3.2. Yesterday at five o’clock we . . . . . . . . . (to advise) much by our colleagues.
3.3. He understood the book only after he . . . . . . (to read) it again.
3.4. I met her while I . . . . . . (to live) in Paris.
3.5. Five years ago our teacher . . . (to be) in London