and catch individual toads by sound.

　　According to Kruse, "Not only will noise pollution bother wildlife, but it won't help our lives either."

9. How do young caribou suffer from aircraft noise?

A. .They can't hear their mothers. B. They can't sleep at night.

C. They are often displaced. D. They receive less food.

10. What would happen if toads and frogs failed to sing in union?

A. They would soon regain their rhythm.

B. They would stop communicating.

C. They might not be able to protect themselves.

D. They might ne unable to hunt in groups.

11. What is the text mainly about?

A. The ways animals communicate with each other.

B. The causes of noise pollution.

C. Animals' reaction to noises.

D. The effects of noise pollution on wildlife.

　　　　　　　　　　　　　　　D

Are you sometimes a little tired and sleepy in the early afternoon? Many people feel this way after lunch. They may think that eating lunch is the cause of the sleepiness. Or, in summer, they may think it is the heat. However, the real reason lies inside their bodies. At that time-about eight hours after you wake up-your body temperature goes down. This is what makes you slow down and feel sleepy. Scientists have tested sleep habits in experiments where there was no night or day. The people in these experiments almost always followed a similar sleeping pattern. They slept for one long period and then for one short period about eight hours later.

In many parts of the world, people take naps in the middle of the day. This is especially true in warmer climates, where the heat makes work difficult in the early afternoon. Researchers are now saying that naps are good for everyone in any climate. A daily nap gives one a more rested body and mind and therefore is good for health in general. In countries where naps are traditional, people often suffer less from problems such as heart disease. Many working people, unfortunately, have no time to take naps. Though doctors may advise taking naps,