题目

  We often hear people talking about a generation gap (代沟). The name is new, but the idea is old. Young people and their parents don’t understand each other. The world has always kept changing. During the second century after Christ a wise man said, “Bury me on my face because in a little while everything will be turned upside down.”       There has always been a gap between generations, but more people talk about it now. Old Mr. Ellis thinks he understands what has happened.      “When I was a boy, I thought the world was a beautiful place. My life was very pleas已知集合A＝{x|x<a}，B＝{x|1≤x<2}，且A∪(∁RB)＝R，则实数a的取值范围是(　　) A．a≤1         B．a<1         C．a≥2         D．a>2