异阶导函数反映函数在不同阶数下的变化特征，揭示函数的深层性质。戏里戏外popo林栀

　　In a class room, a girl is sitting on the desk, solving a math quiz. If she cannot solve it in time, a horrible thing is likely to happen. The clock is ticking but the quiz is not likely to be solved. And her mechanical pencil breaks down. However she has to solve the quiz.