Ⅰ.阅读理解(共15小题；每小题2分，满分30分)
阅读下列短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。
A
Why do people smoke? One reason is that people become addicted to (对……有瘾) cigarettes. The addictive substance in cigarettes is nicotine. When people smoke, the nicotine goes right into the blood stream and makes people relaxed. A smoker's body becomes used to the nicotine and if he stops smoking he feels nervous. Many smokers try to give up smoking, but because of the addiction to nicotine they feel so uncomfortable that they often find it too hard to do so. Another reason is that people only enjoy smoking. Having a cigarette for many people means taking a break. For some people smoking becomes part of certain social rituals (礼节), for example, the cigarette after dinner. Lots of people enjoy smoking because it provides something to do with their hands. Reaching for a cigarette, lighting it, and flicking the ashes is especially comfortable in situations where a person feels nervous.
