C- it would be bias for answer A , many high school student don't have a personal trainer as well as blog posts are not reliable, and parents do not have experience the direct impact . Those are all the reason it can't be any of the others.
A secondary source in when you don't get the information from the person who said let's say you asked what's for lunch today and they told someone to tell you fried chicken but they told you chicken sandwich the answer can change before it gets to you.
