Which factor plays the biggest role in delaying the decision of childhood disease a. high rate of homeschooling b. lack of knowledge of disease c. junk food d. childrens lack of exercise

I personally would say D because the first two are just about having the knowledge of diseases, and junk food can be a problem if there is no exercise to burn off the calories. junk food is bad but i don't think it increases the chances of a childhood disease more than no exercise. 
im not sure if that is what you were asking because the question says '' delaying the decision of childhood disease'' and im not quite sure what you mean by 'decision' in the quation, especially with the answer choices, if you get what i mean.

Ibelieve it's choice d.