单项选择题
Without the help of people from every corner of the world, people in Wenchuan County, Sichuan Province（）recovered very quickly from the May twelfth Earthquake.
A. must not have B. couldn’t have C. may not have D. can’t have
单项选择题 The man showed the boy （）he should play the piano.
单项选择题 A completely new situation will （） when the examination system comes into existence.
单项选择题 （） cave that George has discovered in his lifetime is near the Alps.
