You’d better not _______ these twosentences, otherwise thereaders cannot fully understand you.

When asked to explain _____ he does to make his students so fascinated with his lessons, the teacher paused and thought deeply. [ ]

You should thank PeterIt was he who finally ____ your son to stop smoking and playing computer games

The shopkeeper did not want to sell for he thought was not enough.

have you been a League member— Since the second month I came to this class.