with the human resource market getting competitive,more and more students have sensed the tense atmosphere and felt the necessity of learning more. they are no longer satisfied with what they have learnt at school.they are eager to improve their academic performances and absorb more nutrition to qualify themselves to compete with others.parents also place all their hopes on children,wishing them a bright future. accordingly,a number of tutorial centres which guarantee a good mark mushroomed.they just meet the needs of those students,who poured into the place trgardless of whether they need to do so,some of whom just follow the trend without doing any detective work.as a result,some who have little self-discipline waste time sleeping and reading comics during the lessons.somer who can't arrange their time properly and fit it into their busy schedule don't make progress they have expected. the endless and tiring study without any recreation even affect some s