It is not rare in ____ that people in ____fifties are going to university for further education.
When I handed the report to John, he said that George was the person _______.
He is a man of few words, and seldom speaks until _______ to.
Though I have often heard this song _______. I have never heard you _______ it.
Tony was very unhappy for _______ to the party.
The research is so designed that once _______ nothing can be done to change it.