We all know doing exercise makes us healthy. But many of us don’t know which is better, to exercise in the day or at night. Dr Yang, a famous sleep doctor, advises people to do outdoor exercise for at least 30 minutes a day in the daytime.
Dr Yang has been doing research(研究)on sports and sleep for years. He finds out that those who exercise in natural light for half an hour every day have a better sleep and more energy(能量). Dr Yang himself gets up at 6:30 a.m. Then he usually takes a walk outside. Sometimes, he walks his two dogs in the park in the afternoon with his sunglasses left at home.
Many schools put Dr Yang’s findings into practice. They made it a rule that students should do outdoor exercise once or twice a day. In some schools, students even formed outdoor running clubs. After some time, most students said they benefited a lot from outdoor exercise. Now they sleep better and concentrate(集中)more on their studies.
Some students are now thinking about inviting their teachers to join them in their daily runs.
根据短文内容，回答下列问题。
1. According to Dr Yang, when is it better to exercise, in the day or at night?

2. What is Dr Yang’s research about?

3. Does Dr Yang usually exercise in natural light?

4. How often should students do outdoor exercise in many schools?

5. If you are one of the school teachers, will you join in your students’ daily runs? Why or why not?

1.In the day.
2.Sports and sleep.(Dr Yang's/His research is on/about sports and sleep.)
3.Yes, he does.
4.Once or twice a day./Students should do outdoor exercise once or twice a day.
5.Yes, I will. Because it is good for my health.(开放性试题,言之有理即可)