A、Wash our hands frequently. B、Never rub our nose or eyes. C、Throw away tissues immediately after use. D、Shake hands with our fr

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. (21) 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. (22) 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 a-round.
    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. (23) (25) 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. (24) 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.
21．Which of the following steps will most probably cause one to catch a cold?
22．If you feel a chill，what does it mean?
23．Which of the following is NOT true according to the passage?
24．What should we do to prevent viruses from spreading?
25．Which of the following will most likely get a man to be stricken with a cold？