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 in 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-manifestation”) because they seemed to radically alter one's state of consciousness.
“Substances abuse” (Para. 1) is preferable to “drug abuse” in that ________.
D项意为“除海洛因或可卡因外，许多其他物质也是有害的”。 第一段最后一句指出，许多医生和心理学家常使用“物质滥用”而不 是“药物滥用“这一概念，他们想以此说明：滥用像烟酒这样的物质与 滥用海洛因和可卡因一样有害。
The word “pervasive” (Paragraph 2) might mean ________.
widespread普通的，广泛的。由第二段第一句的冒号后部分所 表达的内容，我们也可以推断出该词的意思。该句句意为：在我们生 活的社会里，医用或社交用物质（药物）广泛存在，如：用阿司匹林制止头痛，用酒交际，早晨用咖啡振作一下精神，抽支烟松弛一下。 因此答案为A。
Physical dependence on certain substances results from ________.
A项意为“长时间无节制地使用它们”。根据第二段第四、五 句，频繁使用某种物质（药物）会使身体对之上瘾或形成依赖。依赖 起先表现为耐药量的增加：要达到满足，需要的剂量越来越多；停止 服用后，一些不舒服的反应就会出现。可见，用药量和用药时间是造 成药物依赖的两个重要因素。
From the last paragraph we can infer that ________.
B项意为“幻觉剂本身就危害健康”。根据第三段第四、五句， 幻觉剂主要影响人的感知觉，以各种方式（包括产生幻觉）将它扭 曲、改变。它们被称作“引起幻觉的药物”，因为它们似乎从根本上改 变了人的意识状态。
Once one was dependent on a kind of substance, he/she________.
根据第二段第四、五句，频繁使用某种物质（药物）会使身体 对之上瘾或形成依赖。依赖起先表现为耐药量的增加：要达到满足， 需要的剂量越来越多。可知A选项为正确答案。