Four students are talking about their favorite sport.

There are 50 students in our class. I made a research (调查). Forty students say they love doing exercise. Most boys play volleyball (排球) together three times a week. But girls think volleyball is not easy for them. They would like to play ping-pong together three times a week.

My friend, Mike, does well in running. He runs quickly in our class. He runs for 30 minutes every day. Tony is good at swimming. He usually goes to the swimming club once a week in winter and four times a week in summer. So he has a good body. Most of my classmates always eat healthy food, for example, meat and vegetables. 80% of them drink milk every day. Twenty students drink milk five times a week. But other students love eating junk food (垃圾食品), especially Sally. It's an unhealthy life way that she does not do exercise. And she is very fat. She always says, "I am going to exercise tomorrow."

“If exercise were medicine（药）, we would all take it,” Shelton, a doctor from Australia once said.

However, according to the WHO（世界卫生组织）, 80% of the children in the world don’t get enough exercise. The WHO thinks that sixty minutes of exercise a day is necessary for children’s growth（成长）. Exercise is good for the heart and lungs（肺）. Also, children will not become fat if they often exercise. And more and more study is showing that exercise can help to lift spirits（振奋精神）and think clearly.

WHO advises（建议）schools and families to ask children to do more exercise. They can do 20 minutes of exercise three times a day to get 60 minutes of exercise. However, it’s not easy. Now many children are difficult to stay away from smartphones or computers. In their free time, they seem to do only three things: eating, sleeping and going online. They’re interested in talking with friends online or playing online games instead of（而不是）doing exercise. The WHO advises that schools and families should think of ways to help children spend less time in the online world and more time in the real world.