Many seniors working on college applications are worried about what major to choose, and how that choice will impact their prospects for admission. Admissions officers know that college students typically change majors two or three times. If you’re applying to a liberal arts college, they don’t usually pay much attention to the major you choose on your application. It’s perfectly acceptable to say you’re undeclared. Some students think by choosing a subject that is under-enrolled at the college, they can increase their chances of being admitted, but they would need to show evidence of serious interest in that subject to have any impact on an admission decision.
University of California campuses don’t typically admit freshmen by major. There are certain programs, like engineering, that have different admission requirements and you do need to apply specifically for admission to those programs. And there are a few schools, like Cal Poly at San Luis Obispo, that admit all students by major, and you need to choose carefully because it may not be easy to change majors once you’re enrolled at the school. But for most students, there is time to choose a major once you’re on campus.