Louis Perkowski, CFA, is an investment advisor for institutional clients in Sarkozi Securities. To comply with the Standards of Professional Conduct relating to diligence and reasonable basis, when selecting external advisors, Perkowski must:（）
A. ensure that Sarkozi Securities has standardized criteria for reviewing external advisors.
B. ensure that the external advisors have the lowest management fee relative to others.
C. ensure that the external advisors have the best historical performance relative to others.
