题目内容：
根据短文内容，回答题。At one time Einstein traveled all over the United States giving a lecture．He traveled by car，and soon became quite friendly with the driver．The driver always listened to Einstein’s lecture，____51____ the great scientist gave again and again．One day，he told Einstein that he knew ____52____ so well that he was sure he ____53____ it himself．Einstein smiled and said，“Why don’t you give the lecture for me next time?”The driver agreed．
That evening，both of them went along to the lecture hall．Nobody there ____54____ Einstein before．As the driver ____55____ his place on the stage everyone clapped．Then he began the lecture．
Sure enough，he did not make a single mistake．It was a great Success，and when it was over， people clapped and clapped．Then he started to leave，shaking ____56____ with everybody，____57____ by Einstein quietly a few steps behind．
Just before they got to the door，a man stopped them and asked the driver a very difficult question．The driver listened carefully．Of course，he did not understand a thing，but he nodded his head as if he ____58____ ．When the man stopped ____59____ ，the driver said that he thought the question was very interesting but really very simple，in fact， ____60____ show how simple the question really was，he would ask his driver to answer it．
________ A．that
B．this
C．which
D．it
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