He invited me to a dance after the show ________ Christmas Eve.(2009·陕西)
_____ when one loses freedom does one know its value.
Little Jim is going to spend his holiday in Paris, _____ lives his uncle.
The problem is not _____ easy. Think _____ over.
It is so difficult a problem that _____ student in this class _____ work it out.
I think he is _____ to win, but I'm not sure.