A new report from a university says 80% of the world's teens don't get enough exercise every day， The report was based on （基于） a research done with about 2 million students aged 11 to 17 around the world．According to the report ， activity standards are different in different countries and they are also different between boys and girls． In China， for example， only 20% of the boys are active enough， compared to 11% of the girls．

Why don't teens go out for exercise？ One main reason is that they always have technology products in their hands or around them． They spend too much time on smartphones，computers and TVs in their free time． Many teens find it very hard to pull themselves away from these devices （设备）．The report says that young people need to do less in the digital world but more in the real world． It advises kids to get at least an hour of exercise every day． This could include running， biking， playing sports， or many other outdoor activities．

   More and more research shows that exercise not only helps the body， but also helps the brain．Besides， doing sports helps kids to make friends． Mark， a sports fan， started to play football when he was six years old． He used to be shy and weak， but now he has become taller and stronger．He gets to know the importance of communicating with his teammates and how to learn from mistakes and failure．And he has made lots of friends with the same interest． They often have football training on the playground． They have more to talk about and enjoy the happiness after training．

根据短文内容，回答下列问题．

（1）How many students around the world took part in the research？ 　　

（2）Are activity standards the same between boys and girls according to the report？ 　　

（3）What does the report advise kids to do？ 　　

（4）When did Mark start to play football？ 　　

（5）Where do Mark and his teammates often have football training？