—How long is it ______ you picked up your badminton training?—It was not until my finance became better last December _____ I started the training.

It was ______ the old clock that the old man spent the whole morning at home.

—I just wonder       that made Mark Twain so famous a writer.—Of course his early experiences.

 Is _______ three hours _______ the poor boy to come to school on foot?

—_____ that he picked up his uncle at the airport?—It was at 6:00 in the afternoon _____ he got off work.