[单项选择]　　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 poison
A. substances can alter our bodily or mental functioning if illegally used
B. "drug abuse" is only related to a limited number of drug takers
C. alcohol and tobacco are as fatal as heroin and cocaine
D. many substances other than heroin or cocaine can also be poisonous