What is your SAT/ACT score? GPA?
You can look at this graph for Elon to see how you fit in.
https://www.thoughtco.com/elon-gpa-sat-and-act-data-786462
What are you getting a D in? Is that something you want to major in?
Here some ideas on how to study differently:
http://talk.collegeconfidential.com/high-school-life/2026961-what-to-do-when-you-arent-doing-well-in-a-hs-class-p1.html