Read the following article and answer the question. Article: Different from popular thoughts, colds are not caused by bad weather. Colds are caused by viruses in the body, and you are better out on the snowy day than you are in a warm room, with your friends, who just may be passing the virus around. If you feel a chill when you are coming down with a cold, you are already sick. A chill is an early sign of the cold. The virus can spread through air when a cold - sufferer coughs or sneezes. Surprisingly, this is not the most usual way of spreading, Many studies have now shown that most colds are " caught " by hands. A cold - sufferer rubs her nose, so spreading the virus to her hand. Then a friend comes to visit her. They shake their hands. The friend then gets something to eat by hand, and several days later she catches a cold. Although some parents pick up their children's tissues and carefully throw them away, they fail to wash their hands. They'll catch the colds, too. Cold viruses can also be spread by objects, for example, telephones, plates. The cold - sufferer as well as other members of the house, by washing their hands often, will stop the viruses from spreading in a way . Question: People catch colds easily because they _ . Answer:
Options: a). rub their noses; b). shake their hands; c). pick up their children's tissues; d). can't often wash their hands;
Answer:
d).