Final answer:
Smoking is responsible for about 50% of the deaths among smokers in the United States and is the leading cause of preventable death, significantly reducing the life expectancy of long-term smokers.
Step-by-step explanation:
Smoking is responsible for a significant portion of deaths in the United States and is the leading cause of preventable death. The Centers for Disease Control and Prevention (CDC) describe tobacco use as a critical preventable risk to human health, with regular smokers dying around 10 years earlier than non-smokers. As many as half of all people who smoke tobacco die from it, which indicates that the correct answer to the student's question is 50%. The life expectancy of long-term smokers can be reduced by up to 18 years, and they have a threefold risk of dying before the age of 70 compared to non-smokers. Smoking is a major cause of various cancers, chronic respiratory disease, and cardiovascular disease, and the risk of dying from lung cancer is significantly higher for smokers.