This study analyzed the patterns of relative clauses (RCs) used on the College Scholastic Ability Test (CSAT), a standardized test for college admissions in Korea. The researchers investigated the Noun Phrase Accessibility Hierarchy and the impact of the antecedent’s animacy on RCs. Also, it was explored how NPs in the subject position of object RCs affected language processing, specifically, the condition where relativizers were omitted and the reasons for producing passive subject RCs. Data were collected from the CSAT and mock tests from 2019 to 2023. The analysis of 622 RCs yielded the following results: First, the frequency of RCs appeared in the following order: subject RCs, object RCs, then OBL. Second, the object RCs showed a preference for inanimate antecedents whereas the subject RCs used did not show a preference for animate antecedents. Third, NPs in the subject position with sentences containing object RCs predominantly took the form of pronouns, with common nouns used less frequently.