Passage Two
The sense of sound is one of our most important means of knowing what is going on around us. Sound has a waster product, too, in the form of noise. Noise has been called unwanted sound. Noise is growing and it may get much worse before it gets any better.
Scientists, for several years, have been studying how noise affects people and animals. They are surprised by what they have learned. Peace and quiet are becoming harder to find. Noise pollution is a threat that should be looked at carefully.
There is a saying that it is so noisy that you can’t hear yourself think. Doctors who study noise believe that we must sometimes hear ourselves think. If we don’t, we may have headaches, other aches and pains, or even worse mental problems.
Noise adds more tension (紧张) to a society that already faces enough stress.
But noise is not a new problem. In ancient Rome, people complained so much about noise that government stop
A. Because the world is becoming more and more noisy.
B. Because they have learned that noise is also a kind of pollution.
C. Because noise is an unwanted waste for human beings.
D. Because people knew little about noise before.
Passage One
Many animals have an excellent sense of smell, which they use in hunting. On the other hand, their eyesight may be poor. Dogs, for example, have poor eyesight and no color vision. They see only shades of gray. But the dog’s sense of smell is extraordinary,
The kind of dog known as Alsatian has 220 million olfactory (嗅觉) cells. Man has five million. Scientists believe that the Alsatian is one million times better than man in finding out odors.
The human sense of smell, however, is really quite good. The average human being can distinguish more than 10 000 different odors.
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