An Auditee Responds to a Corrective Action Request by Stating

An auditee responds to a corrective action request by stating that the problem has never occurred before and is "not the norm for our operation." Which of the following is the most appropriate action for the lead auditor?

A) Note that the deficiency is the result of a random occurrence.
B) Draft a response explicitly requesting a more concise root-cause analysis.
C) Confer with the audit client to assess the appropriateness of the response.
D) Schedule a follow-up audit immediately.