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听力原文: We live in a society in which the medicinal and social use of substances is pervasive: an aspirin to quiet a headache, some wine to be sociable, coffee to refresh oneself in the morning. When do these socially acceptable and apparently constructive uses of a substance become misuses? Most substances taken in excessively will produce negative effects such as poisoning. Repeated use of a substance can also lead to addiction or substance dependence. Dependence is marked first by an increased tolerance, and then by the appearance of withdrawal symptoms when the substance is discontinued. (57)