A、Cigarette ashes. B、Nicotine. C、Tar. D、Not mentioned. C

Why do people smoke?
    One reason is that people become addicted to cigarettes. The addictive substance in cigarettes is nicotine. When people smoke, the nicotine goes right into the blood stream and makes people feel relaxed. A smoker’s body gets accustomed to the nicotine and if he stops smoking he feels nervous. Many smokers try to stop smoking but because of the addiction to nicotine they feel so uncomfortable that they often find it too difficult to stop.
    Another reason is that people simply enjoy smoking. Having a cigarette for many people means taking a break. For some people smoking becomes part of their daily life. Many people enjoy smoking because it gives them something to do with their hands.
    Many people also like the taste of tar in cigarettes. However, it is the tar that causes cancer. While governments and health experts have tried to get people to give up smoking entirely, cigarette manufacturers have tried to keep selling them by producing cigarettes with less tar. Many people in western countries have welcomed these cigarettes since they find it hard to stop smoking but they want to reduce the risk to their health.