四、阅读短文,回答问题。
Mark is a 16-year-old student. He has a very healthy life. However, one year ago, he was not so healthy. From Monday to Friday, he studied every day, but hardly did any sport. He often used the Internet. Although his parents asked him to exercise, he never did. He sometimes helped his mother with housework, but only once a week. At weekends, he liked watching TV. Then the bad result came. He became fat and had few friends. One day, the doctor in his school talked with him. He told Mark to do more exercise because it was good for his body and mind. From then on, Mark decided to change his habits. Now, he does sport more often than before, such as playing basketball and football. He plays less computer games. Doing exercise helps him become healthy and study better. Now he also has more friends.
16. When did Mark have an unhealthy life?
17. How often did Mark help his mother with housework?
18. What did Mark like doing at weekends?
19. How old is Mark?
20. What kind of sports does Mark do now?

16. One year ago. 17. Once a week. 18. Watching TV. 19. He is 16/sixteen years old. 20. He plays basketball and football.