Which of the following is a controllable risk factor of infectious diseases? A. drug abuse B. pollution C. air D. heredity

The correct answer is A. drug abuse.<br /><br />Drug abuse is a controllable risk factor of infectious diseases. By avoiding drug abuse, individuals can reduce their risk of contracting infectious diseases. The other options, pollution, air, and heredity, are not controllable risk factors. Pollution and air quality are environmental factors that can contribute to the spread of infectious diseases, but they are not directly controllable by individuals. Heredity refers to the genetic factors passed down from parents to offspring, which are also not controllable by individuals.