According to IIA Guidance, Which of the Following Statements Best

According to IIA guidance, which of the following statements best justifies a chief audit executive's request for external consultants to complement internal audit activity (IAA) resources?

A) The organization's audit universe is extensive and diverse.
B) There has been an increase in unanticipated requests for advisory work.
C) Previous work provided by the external service provider has been of great quality and value.
D) A recent benchmarking study found that using external service providers is a common practice of similarly-sized IAAs in other organizations.