11．Miss Evans taught physics in a London school．Last month she was explaining to her class about sound，and she decided to test them to see how successful she was in her work．She said to them．Now，I have a sister in Washington If I was calling her on the telephone，and at the same time you were 20meters away and listened to me from the other side of the street，who could hear what I said earlier，my sister r you？And why？ The cleverest boy at once answered，"Your sister，Miss Evans，because electricity （電）travels faster than sound waves（波）．""That's very good．"Miss Evans answered，but then one of the girls put up her hand，and Miss Evans said，"Yes，Betty？" "I don't think so．"Betty said，"Your sister would hear you earlier because when it's eleven o'clock here，it's only six o'clock in Washington．"
53．Miss Evans was teaching her classA． A．a(chǎn)bout sound B．to hear some strange sound C．a(chǎn)bout electricity D．how to say time 54．The cleverest boy thought thatD． A．sound waves travel faster than electricity B．they would hear her sister in Washington first C．Miss Evans's question wasn't right D．Miss Evans's sister would hear her earlier first 55．Betty thought the cleverest boy was wrong，becauseA． A．clocks in Washington showed a different time from hose in London B．electricity was slower than sound waves C．they were only 20meters away from the telephone D．electricity travels as fast as sound waves．
