题目

   One fine afternoon I was walking along Fifth Avenue, ___ 21___  I remembered that it was necessary to buy a pair of socks. Why I wished to buy only one pair is ___22___. I turned into the first sock shop that ___23___  my eye, and a boy clerk who could not have been more than seventeen years old ___24___. What can I do for you, sir? I wish to buy a pair of socks. His eyes were shining. There was a note of ___25___  in his voice. Did you know that you had come into the finest place in the world to buy socks? I had not been aware of that, as I entered the shop ___26___. Come wit△ABC中三个内角为A、B、C，若关于x的方程x2-xcosAcosB-cos2C2=0有一根为1，则△ABC一定是（　　）A．直角三角形B．等腰三角形C．锐角三角形D．钝角三角形