You need Maths B or your local equivalent for most BSc courses. It would also be smart to take Maths C because it will save you having to take makeup courses in first year. Other than that, IMHO pick your best two sciences (ones you're good at and enjoy) and good luck!
Once you're on the university treadmill it's not usually all that difficult to change degrees anyway (a lot of the specialist degrees are really just fancy sounding science degrees with a proscribed course list anyway), so don't stress too much about whether you're picking the right course. If you're unsure about your long term goals, enrol in a general BSc, take a broad range of first year courses and see what you fancy.