Use the Following Information for Questions

Multiple Choice

Use the following information for questions:
In a report by CNN Health News, the headlines read "Study: Junk food raises teens' risk of heart disease." The headlines were based on a study of 249 high school students between the ages of 13 and 18. One researcher said, "more than 80% of those tested were eating a diet that could promote heart disease." Ultrasound was used to measure the thickness of the carotid artery, which, the researcher said, "can be an early indicator of atherosclerosis, an abnormal hardening of the artery walls."
-What was the explanatory variable?

A) Thickness of carotid artery wall
B) Diet
C) Age
D) Physical activity level