A、Because cold viruses can endure unfavorable climates. B、Because winters are wet and cold. C、Because people tend to stay more t

Colds have always been a nuisance, and people have tried many strange ways to cure them, However, none have worked. one Roman historian even recommended kissing the nose of a hairy mouse (29) ! But up till now we are only a little closer to finding a cure for it.
    Scientists have discovered that a cold is not caused by a single virus, but by many. They have proved that people under stress are more likely to catch colds, although why this happens is still unknown (30) . Experiments also showed that women suffer more colds than men. But again, scientists are unable to explain why this is so.
    Another experiment proved that getting cold does not cause colds. For this experiment, one group of human volunteers were showered with water and then made to stand in a windy corridor. Another group remained dry and inside a heated room. While you might expect people in the first group to catch colds more easily, they didn’t.
    one other thing that we now know is that colds are spread by water vapor from breath. This would explain why colds are more common in the winter than at other times: people spend more time indoors closer to other people, and also away from flesh air (31) .