题目

阅读下面短文，从短文后备题所给的A、B、C、D四个选项中，选出可填入空白处的最佳选项。 （淮安）    Wishing to encourage her young son's progress on the piano, a mother took her boy to a pianist's concert on a summer holiday evening. After they found their ____16____, the mother saw two friends in the hall and walked to ___17___ them. It was the boy's first time to come to the hall. He thought it was a good ___18___ for him to explore the wonders of the concert hall. He ___19___ and walked around.  He walked ___20___ a door marked NO ADMITTANCE( 补出下列古诗文中的空缺部分。 丞相祠堂何处寻，锦官城外柏森森。________，________。（杜甫《蜀相》）