The correct answer is C. Documenting findings, actions, outcomes, and lessons learned throughout the process. According to the CompTIA Network+ N10-009 troubleshooting methodology, the final step in the structured troubleshooting process involves documenting everything that occurred during the incident. This includes the root cause, actions taken, changes implemented (such as approved change requests), outcomes of those actions, and any lessons learned.

In the scenario, the key phrase is that leadership is being updated on the results after a breach and an approved change request. This clearly aligns with post-resolution communication and documentation, where technical teams report findings and outcomes to stakeholders. This step is critical for organizational knowledge, audit requirements, compliance, and improving future incident response.

The other options represent earlier steps in the troubleshooting process. Establishing a theory of probable cause occurs early when diagnosing the issue. Establishing a plan of action comes be fore implementing changes. Implementing the solution happens during remediation. However, none of these involve summarizing and communicating results after the fact.

Therefore, updating leadership on results corresponds directly to the documentation and lessons-learned phase of the troubleshooting methodology.