Final answer:
The final engagement communication of an internal audit should be signed by the chief audit executive to represent the audit team and executive oversight. Hence, the correct answer is option 2.
Step-by-step explanation:
The final engagement communication for an internal audit should most appropriately be signed by the chief audit executive. This individual is typically responsible for the overall function of the audit and has the authority to represent the internal audit team.
The auditor and the manager of the activity under review do not both sign to indicate concurrence; the auditor's signature alone would not necessarily represent the perspective of the entire audit team or executive oversight. The chair of the audit committee is usually a member of the board of directors or similar oversight body and would not sign individual audit reports. Hence, the internal auditor, despite having a detailed knowledge of the report, does not sign alone to ensure that there is representation from the leadership of the internal audit function.