Do I have to do ROTC to become a US Army Infantry Officer?

I want to be a US Army Infantry Officer, however my parents do not want me doing ROTC in college. They want me to focus completely on school and athletics. Could I just do Officer Candidate School after college instead? Does that weaken my chances of getting the Infantry MOS? Also, does your B.A. affect what MOS you get? I am planning on Finance, which I do not believe has too much to do with Infantry, but I am dying to be an Infantry Officer. Thanks.