Ⅱ．选择方框内的短语，并用其恰当的形式填空
hear from; by the way; lose one's way; at the age of; take part in; do one's best
【小题1】If you don't ______, you will never know what you can get.
【小题2】Bob is a smart boy. He started reading books ____________ five.
【小题3】____________, do you have any plans for this weekend?
【小题4】The news said a bus driver ____________ because of the heavy haze（雾霾）.
【小题5】Mr. Li was glad to ______ his son.
【小题6】Why not ______ some after-class activities? You can make new friends.