I'm studying A-level in sandwich course(whole A-level in 3 terms) ,I started 2weeks ago and I chose Mathematics and Physics ,besides, I wanna do physics in one of the top universities of England so , I need one more subject . which subject is suitable as third subject for me with respect to that I'm doing whole A-level in just 3 terms. e.g. chemistry , it , computer and other stuff like this?