—You may find the key to the math problem on page 107.—Ah, it’s so simple. I wonder why I _____ of that.
Children in the countryside can receive education ________ free since last year.
--- I can’t find Xiao Ping. Where did you see him this morning? --- In the reading room _________ he often studies in.
I regret _________ going on a holiday to France because of the bad weather last week.
All __________ can be done has been done.
--- What do you think of the film Schindler’s List? --- This is the best film _______ I have ever seen.