The best course of action for the IS auditor is A. Escalate to IT management for resolution. This is because IT management is responsible for overseeing and coordinating the IT activities and functions within the organization, and ensuring that they comply with the audit findings and recommendations1. IT management can help resolve the issue of finding ownership by:

Clarifying and communicating the roles and responsibilities of each IT team, and how they relate to the finding and its remediation2.

Evaluating and assigning the finding to the most appropriate IT team, based on their expertise, authority, and availability2.

Providing guidance and support to the assigned IT team, and monitoring their progress and performance in remediating the finding2.