The correct answer is C. the impression you make on admissions officers during an on-campus interview.
The rest of the options are quite objective - these officers have a certain set of rules that every applicant has to meet in order to be enrolled in a university. However, what is subjective about this is the effect that the applicant may have on the officers - the better the impression is, the more likely it is that he or she will be admitted into their preferred university.