People today are still talking about the generation gap(代沟). Some parents complain that their children do not show them proper respect, while children complain that their parents do not understand them at all. What has gone wrong Why has the generation gap appeared One important cause is that young people want to choose their own life style. In more traditional societies, when children grow up, they are expected to live in the same area as their parents. to marry people that their parents like. and often to continue the family occupation. Parents often expect their children to do better than they do, to find better jobs, to make more monkey, and to do all the things that they were unable to do. Often, however, the high wishes that parents place on their children are another cause of the generation gap. Finally, the high speed of social changes deepens the gap. In a traditional culture, people are valued for their wisdom, but in our society today the knowledge of a lifetime may be out of use overnight(隔夜). In today’s society, the knowledge of a lifetime______ .