I see many people have had questions regarding what options you can take and your classification as a Natural Science student. This is what I have snapped up from Websites, Other students , Application forms, prospectus etc etc..
1: You are not commited to do physical options if you put physical on your application form. They just ask you to specify cus it helps them giving offers so that they have an aproximately equal amount of biological and physical students. Also, it tells them what subjects you want in your interview.
2: Once you get in you can chose options quite freely. For some courses you may be requiered to have certain subjects in yoru previosu education however. Also, Im not certain that they will let you do just any combination you like. Basicly, you say what you want to do, and they see if they can make it happen or if they want to recomend / force you to do something different. I would not worry to much about this, they pretty much want students to tell everyone how great cambridge is once theyve finished, so they will most likely try to help you pick a course which you find interesting.
I just got an offer for Sidney Sussex collage. They asked for an IB diploma with 7 7 6 in my High level subjects and 39 points total (Yiiikes).