What are the subjects that one must learn while an undergraduate to pursue an academic career in Biophysics?
Specific biological domain knowledge will be something that you will learn in the course of doing research, and can be hard to predict at this point in your studies, because you have no idea what kind of graduate program you'll be admitted to or the specific research field of your prospective advisor. 

Therefore, while all of those directions sound fine and won't be wasted if you choose them, I would lean towards the more foundational topics, i.e. Chemistry or Computer Science, that you could use no matter what direction you took in the future. Another option would be statistics, since nearly any biophysics research involving experiments will need a very solid understanding of stats to design experiments with high statistical power, and to make sense of the resulting data without getting tricked by spurious correlations.