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  3. Drugs can be divided into three main groups: those that a person can buy without a prescription, those that a person needs a doc

Drugs can be divided into three main groups: those that a person can buy without a prescription, those that a person needs a doc

admin2010-09-10  40
问题     Drugs can be divided into three main groups: those that a person can buy without a prescription, those that a person needs a doctor’s prescription for, and those that are illegal.
    Two popular nonprescription drugs are caffeine (咖啡因) and alcohol. Caffeine is found in coffee, tea, chocolate, and cola drinks. It is a mental stimulant; it stimulates the central nervous system and makes people feel alert. Students, for example, often find they can study better if they have a cup of coffee. On the other hand, caffeine can also make people nervous and irritable. If people drink too much caffeine, they may have trouble sleeping.
    Alcohol is a depressant; it depresses the central nervous system. When people drink, they have less control over their actions. They cannot walk in a straight line and they cannot drive as well as when they are alcohol-free in their blood. People who drink a great deal sometimes fall into a deep sleep. Later, they may wake up with a strong headache.
     In addition to these nonprescription drugs, there are two major categories of prescription drugs: stimulants and depressants. The depressants include morphine(吗啡), which is used as a pain killer. The most common stimulants are amphetamines (苯丙胺). Doctors used to prescribe amphetamines as diet pills; however, they found that amphetamines can have serious side effects. They can make a patient very nervous, and when the drug wears off, the patient may feel very depressed. Doctors still give amphetamines  to people with narcolepsy, an illness that causes sudden, uncontrollable attacks of sleep.
    The largest class of illegal drugs are hallucinogens, drugs that change the way a person thinks and cause hallucinations, or visions. For some people, marijuana(大麻) is a mild hallucinogen. Marijuana generally brings a pleasant feeling. However, when people smoke marijuana, they sometimes can not concentrate very well on their activities, such as their work or driving.
What does the word "hallucination" mean?
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答案Vision
解析 连词在阅读理解中起着十分重要的作用。巧妙地利用连词，我们对难句的理解会变得更轻松；有时这些“不起眼”的词甚至在理解中起决定性作用，达到事半功倍的效果。连接词在英语中也称作“signal words”(提醒词)，单从称谓上就可看出其作用是不可低估的。
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