Which of the following should be implemented to promote independence of the internal audit activity?

To promote the independence of the internal audit activity, it is required that the chief audit executive reports functionally to the board. This structural alignment helps ensure that the internal audit function is not unduly influenced by management, which might be the subject of audits, and can freely report on its findings and recommendations without fear of reprisal.

The IIA's International Standards for the Professional Practice of Internal Auditing on independence and objectivity.