The correct answer is C because Standard V (A): Diligence and Reasonable Basis requires members and candidates involved in the selection of external advisers or managers to ensure their firms have standardized criteria for reviewing these advisers. Such criteria may include reviewing the adviser's code of ethics, compliance procedures, quality of published return information, and adherence to investment strategies. This standard emphasizes the importance of thorough due diligence in selecting external managers, which aligns with the requirement described in the question. Standards III (C) and I (B) are not relevant to this specific requirement.