Which of the Audit Procedures Listed Below Would Be Least

Which of the audit procedures listed below would be least likely to disclose the existence of related-party transactions of a client during the period under audit?

A) Reading 'conflict-of-interest' statements obtained by the client from its management.
B) Scanning accounting records for large transactions at or just prior to the end of the period under audit.
C) Inspecting invoices from law firms.
D) Confirming large purchase and sales transactions with the suppliers and/or customers involved.