Introduction H raclitus, an ancient Greek philosopher,once said:"You can't step twice into the same river."In this world, the only thing that is constant and doesn't change is change itself,which describes one of the important characteristics of our modern society. 制价爱行蜀易大考Introduction Introduction Heraclitus, an ancient Greek eraclitus, an ancient Greek philosopher, once said: philosopher, once said: “You can't step You can't step twice into the same river. twice into the same river.”In this world, In this world, the only thing that is constant and the only thing that is constant and doesn ’t change is change itself, which t change is change itself, which describes one of the important describes one of the important characteristics of our modern society. characteristics of our modern society