This document discusses adjective clauses and the use of relative pronouns like who, whom, and that. It explains that in some clauses the relative pronoun is the subject, while in others it is the object. When the pronoun is the object, it can be omitted, but when it is the subject it cannot be omitted. The document provides examples and concludes with key points about using who, whom, or that as the subject or object of an adjective clause.