What factors may contribute to aging? a. cells stop dividing after 50 divisions. b. cells become more and more damaged. c. genes “tell” cells to stop dividing. d. all of the above

Other possibly contributory lifestyle factors include alcohol consumption, stress, diet, exercise, disease, and medication. In summary, the genetic influences on aging may be highly overrated, with lifestyle choices exerting far more important effects on physical aging.

I think it's D. all of the above

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.