Technically, any substance other than food that alters our bodily or mental functioning is a drug. Many people mistakenly believ

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问题     Technically, any substance other than food that alters our bodily or mental functioning is a drug. Many people mistakenly believe the term drug refers only to some sort of medicine or an illegal chemical taken by drug addicts. They don’t realize that familiar substances such as alcohol and tobacco are also drugs. This is why the more neutral term substance is now used by many physicians and psychologists. The phrase "substance abuse" is often used instead of "drug abuse" to make clear that substances such as alcohol and tobacco can be just as harmfully misused as heroin and cocaine.
    We live a society in which the medicinal and social use of substances(drugs)is pervasive: an aspirin to quiet a headache, some wine to be sociable, coffee to get going in the morning, a cigarette for the nerves. When do these socially acceptable and apparently constructive uses of a substance become misuses? First of all, most substances taken in excess will produce negative effects such as poisoning or intense perceptual distortions. Repeated use of a substance can also lead to physical addiction or substance dependence. Dependence is marked first by an increased tolerance, with more and more of the substance required to produce the desired effect, and then by the appearance of unpleasant withdrawal symptoms when the substance is discontinued.
    Drugs(substances)that affect the central nervous system and alter perception, mood, and behavior are known as psychoactive substances. Psychoactive substances are commonly grouped according to whether they are stimulants, depressants, or hallucinogens. Stimulants initially speed up or activate the central nervous system, whereas depressants slow it down. Hallucinogens have their primary effect on perception, distorting and altering it in a variety of ways including producing hallucinations. These are the substances often called psychedelic(from the Greek word meaning "mind manifesting")because they seemed to radically alter one’s state of consciousness.  
Physical dependence on certain substances results from______.

选项 A、uncontrolled consumption of them over long periods of time
B、exclusive use of them for social purposes
C、quantitative application of them to the treatment of diseases
D、careless employment of them for unpleasant symptoms

答案A

解析 本题可参照文章第2段的倒数两句话。从中可知,反复使用一种物质也会导致对该物质的生理上瘾或对药物依赖;依赖性起初表现为耐受性不断增强,需要越来越多的药物才能获得所需的效果,一旦停用,就会产生不舒服的症状。据此可知,对某些物质的生理依赖,是由于人们长时间、大量使用这些物质所造成的。A项与文章的意思相符;B项不正确,文中是说“喝一点酒以增进友谊”,但并没有说这会导致对酒的生理依赖;C项和D项明显不是对某些物质生理依赖的原因。综上所述,只有A项为正确答案。
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