Final answer:
Smoking is the major cause of chronic respiratory disease, cardiovascular disease, and cancer, and it has negative effects on various other parts of the body. It is dose and duration sensitive, meaning the more and longer someone smokes, the greater the health risks become.
Step-by-step explanation:
Smoking is the major cause of chronic respiratory disease as well as cardiovascular disease and cancer. Exposure to tobacco smoke by smoking or by breathing air that contains tobacco smoke is the leading cause of preventable death in the United States. Regular smokers die about 10 years earlier than nonsmokers do. The Centers for Disease Control and Prevention (CDC) describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of [early] death worldwide."
Smoking has a wide range of negative effects on the body, not just limited to the lungs and respiratory system. It increases the risk of developing chronic kidney disease, infectious diseases, and various cancers. Smoking is also dose and duration sensitive, meaning the more and longer someone smokes, the greater the health risks become.
Therefore, the correct answer to the question is a. dose and duration sensitive.