完形填空。

    Mr. Clarke works in a middle school. He likes reading and often 1 some books from the library. He2 to the radio every morning and reads 3 after supper. So he knows much and teaches well. His 4 worship(崇拜)him very much. Mike， Mr. Clarke's little son， is only nine. He5 likes reading books. And he often asks his father some questions. Mr. Clarke always thinks he’s too6to understand him and chooses7ones to answer. Of course the boy is not satisfied with(对……满意)it. One day Mike read8about the lights and was9 it. When his father told him to do some housework， he went on thinking of it. He asked him 10 questions， and his father answered all. Then his father said proudly， “Fathers always know 11 than sons!” The boy thought for a while and said， “12.” His father asked， “Oh? Why?” Mike didn't answer， and asked，13， “Who invented the lights?”“14”answered Mr. Clarke. “Why didn't his father invent them， then? ”Looking at his son， Mr. Clarke didn't know 15 to answer!