Do you know that it is your immune system (免疫系统) working against the virus that makes you uncomfortable when getting a cold, but not the virus itself? So when you have got a strong immune system—and the virus is strong enough too—you will possibly get terrible cold symptoms (症状) such as having a headache, having a high fever, sneezing or coughing,

    Vitamin C won't stop a cold. It is said that Vitamin C works by increasing white blood cells.

However, many tests have shown that it does not prevent colds. At best, it only reduces the time of symptoms.

    Staying indoors won't protect you. One of the most likely sources (根源) of cold viruses is your computer mouse or desk. A study of the cold virus in offices found that 46 per cent of computer mice and 45 per cent of telephones had cold viruses on them.

    Wearing warm clothes won't protect you. Colds are more common in autumn and winter. That's because the cool, wet and cold weather drives people indoors, where viruses may more easily jump from one person to the next. And the distinct peak (高峰期) in colds is in September and February, which likely because of the return of students to schools and colleges after the summer and winter holidays.

    Old wives are right about chicken soup. Grandmothers' chicken soup is an old cure for colds for a long 6me. Scientists say it is true. Chicken soup does help cure a cold, so many wives usually cook chicken soup for their family members in cold winters.

29. According to the passage, when your immune system is working against the virus, you don't   have cold symptoms like ________.

     A. headache      B. stomachache       C. sneeze         D. cough

30. Which of the following ways can really help cure colds?

     A. Staying indoors.

     B. Wearing more clothes.

     C. Drinking some chicken soup.

     D. Eating some fruit with Vitamin C.

31. Why are colds more common in autumn and winter?

     A. Because students return to school.

     B. Because the weather is cool, wet and cold.

     C. Because people don't drink chicken soup.

     D. Because people use computers or telephones more often.