Mr. Clark works in a middle school. He likes reading and often borrows some books the library. He listens to the radio every morning and reads all kinds of (newspaper) after supper. So he knows much and teaches well. His students like (his) very much. Mike, Mr. Clark's little son, is only nine. He also likes books. And he often asks his father some questions. Mr. Clark always thinks the boy is too young (understand) them and chooses the easiest ones to answer. Of course the boy is not pleased with it.

    One day, Mike read something about the lights and was (interest) in it. When his father told him to do some housework, he went on thinking of it. He asked Mr. Clark a few questions, and his father answered all. Then his father said (proud), "Fathers always know more sons do!"

    The boy thought for while and said, "I don't think so."

    "Oh? Why?"

    Mike didn't answer but asked a question instead, "Who (invent) the lights?" "Thomas Edison." answered Mr. Clark.

    "Why didn't his father invent them?" (look) at his son, Mr. Clark didn't know how to answer the question!