Section 18. Statements made by persons to Commission.

No statement made by a person in the course of giving evidence before the Commission or any officer or agency or the person referred to in section 9, shall subject him to, or be used against him, in any civil or criminal proceeding except a prosecution for giving false evidence by such statement: Provided that the statement— Statements made by persons to Commission. (a) is made in reply to a question which is required by the Commission or such officer or agency or such person to answer, or (b) is relevant to the subject matter under investigation.