Police Cannot Legally Gain Access to a Student's Living Quarters

Police cannot legally gain access to a student's living quarters on a private university for the purpose of searching, even if they have permission of university administration, unless they have a warrant issued. Why is this statement true?

A) Because the search is conducted by police, the purpose is a criminal investigation.
B) Because the university is private, not public.
C) Because college and university students are afforded absolute protection from unwanted searches and seizures.
D) Because there is no distinction in Fourth Amendment law between private and public universities.