参考答案：The relative pronouns for personal antecedents used in the restrictive relative clauses include who or that as subject, who, whom or that as object and which, not who as the relative pronoun that plays the role of subject complement or object complement.
The relative pronouns for non-personal antecedents in the restrictive relative clauses refer to that or which.
In non-restrictive relative clauses, who is used for the personal antecedent, and which for the non-personal antecedent. But the relative pronouns as subject complement or object complement, only which can be used. That can not be used in the non-restrictive relative clauses.
