Final answer:
Cardiovascular diseases account for approximately 30% of deaths in the United States, making it the correct answer to the student's question.
Step-by-step explanation:
Diseases of the heart and blood vessels, or cardiovascular diseases (CVD), are a significant health concern and the leading cause of death in the United States. Specifically, cardiovascular disease accounts for about 30% of deaths in the United States, which confirms that the correct answer to the student's question is (b) Approximately 30%. Heart disease's prevalence is largely due to factors like sedentary lifestyles, high trans-fat diets, and other risk factors such as smoking, obesity, diabetes, high blood cholesterol, and lack of exercise.