Mr. Green works in a high school. He likes reading and often borrows some books from the library. He keeps reading newspapers after supper. So he knows much and teaches well. His students loves him very much. Mike, his little son, is only nine. He also likes reading books. And he often asks his father some questions. Mr. Green always answers difficult ones. One day Mike read something about phones and he was interested in it. He asked his father a few questions, and his father answered all.  His father said, " Fathers always know much, but sons always know little!" The boy thought for a minute and said," I don't agree with  you." "Oh? Why?" Mike didn't answer but asked, "Who invented the phone?" "Bell." answered Mr. Green. "Why didn't his father invent them?" Looking at his son, Mr. Green didn't know how to answer it. From the story ,we know that Mike is a   _  boy.
lazy seven-year-old clever stupid( ).