Hey.

This question needs to be answers by you yourself. You better know what your capabilities are and what are the areas you lack in. The interests you have will help you determine the subject you must choose. The subject which interests you the most and which you find easy to concentrate with should be opted as your subject in B.Sc (hons).
Study and do a research on the future prospects of the subject, colleges which would provide you the maximum opportunities, and the subject matter to be taught there before taking a final decision.

Hope this helps. All the best.