答案：It can be seen easily from the above chart that American students spend 72 minutes on physical activity per day, and those in South Korea spend 42 minutes. However, Chinese students have only 12 minutes for physical activity per day. Why is so little time taken to work out for Chinese students? In my opinion, there are several reasons leading to this situation.First, many Chinese schools attach much importance to study, and almost all the time is spent on lessons. Besides, students are made by parents to concentrate on their study even when they get back home. In addition, today smart phones are popular among students, and many students are unwilling to exercise after a long day's hard work. On the contrary, they prefer to be lost in their smart phones. Therefore, there is little time left for their physical activity.As far as I'm concerned, both the Education Department and parents are responsible to allow the students more time for physical activity, and students themselves should also spend less time on phones and more time on exercise