____ to the surprise of the teachers, the naughty boy turned out to be the person who saved the dying girl. 

He could have finished it on schedule, but ________ he fell behind.

Although modem organic food has become very popular, many people can' t figure out the difference between organic foods and ______ grown foods．

If you smoke a cigarette every day, you will _____ become addicted to smoking．

When we think of communication , we _________ think of using words---- talking face to face, writing messages, and so on .