题目内容：

Some educators told us that more years of school could help students get higher scores on intelligence tests. That was a finding of a study of teenage males in some countries. Now, another research shows that physical activity may help students do better in their classes.

The research comes as educators in some countries are reducing time for activities like physical education. They are using the time instead for academic（学术的）subjects like math and reading. The studies appeared between 2008 and 2014. They included more than 55, 000 children, aged 6 to 18.

Amika Singh:“ According to the results of our study, we can conclude that being physically active is beneficial for academic performance. There are, first, Physiological explanations, like more blood flow, and so more oxygen to the brain. Being physically active means there are more hormones(荷尔蒙)produced like endorphins(内啡肽). And endorphins make your stress level lower and your mood improved, which means you also perform better.”

Also, students taking part in organized sports learn rules and how to follow them. This could improve their classroom behavior and help them keep their mind on their work.

The study leaves some questions unanswered, however. Ms. Stash says it is not possible to say whether the amount or kind of activity affected the level of academic improvement. This is because of differences among the studies.

The researchers said they found only two high-quality studies. They needed more high-quality studies to confirm (证实) their findings. They also pointed out that “results for other parts of the world may be quite different.”

Still，the general finding was that physically active kids are more likely to do better in school. Ms. Singh says schools should consider that finding before they cut physical education programs. Her paper on “Physical Activity and Performance at School” is published in the Archives of Pediatric and Adolescent Medicine.

1.The passage mainly tells us that ________.

A. a research on physical education has been done by the researchers

B. there is a possibility that physical activity leads to higher grades

C. the amount or kind of activity directly affects academic level

D. the research shows that the children aged 6 to 18 don't do sports

2.Which of the following is TRUE?

A. Being mentally active is good for academic subjects.

B. The more hormones you have, the more stressed you will get.

C. The researchers have found many high-quality studies to prove the research.

D. The educators in some countries think studies, not exercise, mean much to students.

3.The underlined sentence in Paragraph 6 probably means ________.

A. good marks result from high-quality study.

B. findings are probably different in different areas.

C. physical activity will spread all over the world.

D. academic performance depends on the surroundings.

4.What's the purpose of writing the passage?

A. To call our attention to the sports at school.

B. To introduce all types of physical activities.

C. To represent the academic performance.

D. To improve students’ health.