D. a research article that includes interviews with teenage athletes.
D is the closest thing to a primary source because it includes interviews with the actual teenage athletes. Because they are experiencing the topic, they are the primary source on that topic. Got it right on Edmentum.
A sounds reliable, but it is incorrect. While they might have knowledge on the subject, it is secondary knowledge because they aren't actually experiencing it.
B is wrong because the famous athlete isn't actually experiencing it, so they're secondary, and it's not related to sports, mental health, or girls.
C is wrong because op-eds may be unreliable, a teacher isn't a primary source, depression in teenage girls is not directly related to the effect of sports.
Got it right on Edmentum.