五、阅读理解
You are thirsty after playing sports or riding home from school. A cold drink may be great. But something that looks cool may not be good for your health.
There are plenty of "energy drinks" on the market. Most of them have beautiful colours and cool names. But after a careful check, you may find that most energy drinks have lots of caffeine（咖啡因） in them.
These drinks are mainly for young people, students, busy people and sports players. Makers sometimes say their drinks can make you feel better at sports and keep you awake. But be careful not to drink too much.
Too much caffeine are bad for health. Because of this, the Olympic Games have limited its use. Caffeine in most energy drinks is almost as strong as that in a cup of coffee or tea. Just one bottle of energy drink can make you excited, have difficult sleeping and can even cause heart problems. Scientists say that teenagers should be stopped from taking drinks with a lot of caffeine in them.
So we should stay away from the energy drinks to keep healthy.
29. What does the underlined word "limited" mean in Chinese?
A. 限制
B. 唤醒
C. 扩大
D. 推广
30. What does the third paragraph mainly talk about?
A. The uses of caffeine.
B. The dangers of too much caffeine.
C. The reasons for heart problems.
D. The causes of difficult sleeping.
31. What's the main idea of the passage?
A. What's the use of energy drinks?
B. Who can drink energy drinks?
C. What's in energy drinks?
D. What should we drink?

29. A 30. B 31. C