The answer is C. A drug is any substance that alters the normal functioning of the body.
A drug is any substance other than the nutrients essential for body changes the normal functioning of the body. It may be physiological or biological which is temporary. A drug is used in the diagnosis, treatment or prevention of a disease to relief the discomfort. A drug producing a state to relief the discomfort. A drug producing a state of casual when used in continuation or in excessively causes addiction known as drug abuse.