What is best changes based on your point of view.
If I was a college administrator, I may prefer “A”, as it’s the easiest to put in place and to manage (I screen students during the freshman screening process), while simplifying capacity management (by major).
If I was a student, I would prefer “C”, as it ensures I get the major I want, can easily switch majors (up until my junior year), and all I need to do is perform well in class.