完形填空。 Mr Green works in a middle school. He 1 a teacher. He likes reading and often 2 some books from the library. He keeps 3 to the radio every day and reading texts after supper.So he knows much and teaches 4 . His students like him very much.Mike, Mr Green's little son ,is only nine. He often reads when his father is 5 . And he often asks him some questions. Mr Green always thinks he is too 6 understand them and chooses 7 one to answer. Of course the boy is not satisfied (满意) with it. One day, Mike read 8 about the electric lights and was 9 it. When his father told him to do some homework, he went on thinking of the book. He asked his father 10 questions,and his father answered all. Then the father said proudly, 'Fathers always know 11 than sons!' The boy thought for a while and said, ' 12 !' 'Oh? Why?' Mike didn't answer and 13 instead 'Who invented the electric lights?' ' 14 .' answered Mr Green. 'Why didn't his father inwent them,then?' Looking at his son, Mr Green didn'tknow 15 to answer! (     )1.A.am (     )2.A.buys (     )3.A.listening (     )4.A.well (     )5.A.sleeping (     )6.A.silly (     )7.A.the easiest (     )8.A.a newspaper (     )9.A.surprised (     )10.A.a little (     )11.A.no (     )12.A.Happily (     )13.A.asked (     )14.A.Washington (     )15.A.when B.is B.borrows B.watching B.bad B.at school B.young B.the hardest B.a book B.worried B.little B.more B.Not always B.swam B.Bill Gates B.why C.are C.lends C.hearing C.maths C.eating C.clever C.the best C.a test C.interested in C.few C.less C.Who C.sang C.Mr Green C.how D.been D.keeps D.talking D.French D.at home D.old D.the worst D.a piece of paper D.sure about D.many D.much D.Nothing D.danced D.Edison D.where