题目内容：

Why do people smoke? One reason is that people become addicted(成瘾) to cigarettes. The addictive substance(物质）in cigarettes is nicotine(尼古丁). When people smoke, the nicotine goes right into the blood stream and makes people feel comfortable. A smoker's body gets used 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____.

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 certain social rituals (礼仪), for example, sending the cigarette after dinner. Many people enjoy smoking because it gives them something to do with their hands. Reaching for a cigarette, lighting it and flicking (弹掉) the ashes are special comfort in a situation where they feel nervous.

Many people also like the taste of tar (焦油) in cigarettes. However, it is the tar that causes cancer. While governments and health experts have tried to get people to give up smoking completely, cigarette manufacturers (生产商) have tried to keep selling them by producing cigarettes with less tar. Many people in western countries have welcomed these cigarettes since they found it hard to stop smoking and wanted to reduce the danger to their health.

1.According to the passage, what gets people into the habit of smoking?

A. The cigarette.    B. Nicotine.    C. Tar.    D. Blood.

2.What do the underlined words "to do so" mean?

A. They mean "to stop smoking".

B. They means "to make people feel comfortable".

C. They mean "to get used to the nicotine".

D. They means"to become addicted to cigarettes".

3.Why do people welcome low-tar cigarettes?

A. Because they taste better.

B. Because they are cheaper.

C. Because they are less harmful.

D. Because they are easy to be made.

4.Which of the following sentences is TRUE, according to the passage?

A. Smokers continue smoking because smoking is very interesting.

B. Tar in cigarettes causes cancer.

C. In order to look cool, many people enjoy smoking.

D. Many people in western countries welcome the cigarettes with more tar.