1. When does physical drug dependence happen?

Physical dependence occurs when the brain adapts to the effects of a drug and develops tolerance. In other words, an individual will require more and more of the drug to achieve the initial positive effect and will rely on continued use of the drug to prevent painful and uncomfortable withdrawal symptoms

exposure to hazardous carcinogens and toxic substances can cause breathing problems, such as copd and various types of cancer. it also increases the risk of heart attacks and strokes and has serious (but no less unattractive) side effects, such as aging, yellow teeth, a terrible smell and damage to the vocal cords.

answer (c) by causing social withdrawal;