Many cultures have different ideas about why people catch colds. For example, in the United States, some people think that you can catch cold if your （1） get cold. So, mothers tell small children to wear（2）boots(靴子) in the winter. In other places, including parts of the Middle East, some people believe that strong winds cause colds. So, on trains and buses, people usually don’t like to sit（3）open windows. In parts of Europe, some people think that wearing wet clothes will give you a cold. They say that after you go （4）, you should quickly put on dry clothes. Today, scientists know that colds are caused by viruses(毒). But the old ideas are still very strong, and many people still follow them to （5）getting ill.
1（）
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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