正解:C
By accepting a role as an engagement supervisor on a highly specialized and technical engagement for which she did not have the expertise, the internal auditor violated the fundamental principle of competency as outlined in The IIA's Code of Ethics. The principle of competency requires internal auditors to perform audit services with the necessary knowledge, skills, and experience. Accepting an assignment without the required expertise undermines the quality and reliability of the audit work.
References:
* The IIA Code of Ethics: "Internal auditors shall engage only in those services for which they have the necessary knowledge, skills, and experience."
* The IIA Standards: Standard 1210 - Proficiency: "Internal auditors must possess the knowledge, skills, and other competencies needed to perform their individual responsibilities."