21.

  1. To stay in a very warm room with a lot of people.
  2. To expose oneself to severe weather.
  3. To play outdoors long when it is snowing.
  4. To wait for a bus on a cold and windy day.

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22.

  1. You'll catch a cold sooner or later.
  2. You've already come down with a cold.
  3. There are viruses hidden in your body.
  4. The room is not warm enough for your health.

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23.

  1. It is generally believed that colds are caused by exposure to cold weather.
  2. Most colds are "caught" by hand contact.
  3. Cold virus will keep alive for several hours once it leaves human body.
  4. Cold virus can spread around only through the air.

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24.

  1. Wash our hands frequently.
  2. Never rub our nose or eyes.
  3. Throw away tissues immediately after use.
  4. Shake hands with our friends instead of kissing them.

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25.

  1. A cold-sufferer is staying with him in the same room.
  2. The viruses have been exposed to the air for over 3 hours.
  3. He dropped in a warm room.
  4. He shakes hands with a cold-sufferer.

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There are some steps you can take yourself to avoid catching a cold. Contrary to popular belief, colds are not caused by exposure to severe weather. Colds are caused by viruses harbored in the body, and you're better off out on the ski slopes or even waiting for the bus on a snowy day than you are in a toast warm room, surrounded by friends, co-workers, or fellow students, who just may be passing the virus around. If you feel a chill when you're coming down with a cold, you're already sick. A chill is an early symptom: it's the cold that caused the chill, not the other way around.

While the virus can spread through droplets propelled into the air when a cold-sufferer coughs or sneezes, surprisingly, this is not the most common route of transmission. Numerous studies have now shown that the overwhelming majority of colds are "caught" by hand contact. A cold-sufferer rubs her nose, thereby transferring the virus to her hand. Then a friend comes to visit. "Don't kiss me," she cautions, so the friend steps back and presses her hand. The friend then wipes her own nose or eye -- and several days later is stricken with a cold. Or parents pick up their child's discarded tissues and carefully throw them away but fail to wash their hands afterward.

Cold virus also can be transferred to objects -- telephones, towels, plates -- and remain infectious for up to three hours. Frequent hand washing -- on the part of the cold-sufferer as well as other members of the household -- will minimize the spread of viruses in this way.