According to the PMBOK Guide, specifically within the Direct and Manage Project Work and Perform Integrated Change Control processes, the formal mechanism used to address a defect is a Change Request.
* Defect Repair: This is a specific type of change request. It is an intentional activity to modify a nonconforming product or product component.
* The Process Flow: When a defect is identified during execution, it must be documented. Even though the project manager is taking responsibility and the action is necessary, it must still pass through the change control system to ensure the impact on scope, schedule, and cost is assessed.
* Documentation: The " correct documentation " mentioned in the question refers to the formal change request form and the subsequent update to the Change Log once the repair is approved and initiated.
Analysis of other options:
* B and C. Risk response / Risk management plan: Risk management deals with uncertain future events (threats or opportunities). A defect is an issue that has already occurred (a " fact " in the present). While a risk response plan might have anticipated the possibility of defects, the actual act of repairing one that has been found is handled through change control.
* D. Lessons learned: While the project manager should document the defect and how it was handled in the Lessons Learned Register to prevent future occurrences, " Lessons Learned " is a knowledge management activity, not the process used to physically perform the repair during execution.
Per PMI standards, all Defect Repairs, Corrective Actions, and Preventive Actions must be processed as Change Requests to maintain the integrity of the project baselines.