A、People will become seriously ill. B、People will become dependent on them. C、They will make people feel tired. D、They will give

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 neutral term ’substance’ is now commonly 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 substance is widespread. For example, an aspirin is often used to quiet a headache. Wine is thought to be necessary for social occasions. Some people drink coffee to get going in the morning. Others consider a cigarette is good for the nerves.
    When do these socially acceptable and obviously constructive uses of a substance become misuses? First of all, most substances taken in excess will produce side-effects such as poisoning or intense perceptual distortion. 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.