Near project completion, a key stakeholder did not approve because required deliverables were not functioning as expected. What should the project manager do next?

The correct answer is to review the requirements traceability matrix. This document links requirements to deliverables, tests, and other project artifacts. If deliverables are not functioning as expected, the RTM helps identify which specific requirements were not met, enabling the project manager to trace back to their origin and understand the discrepancy. Reviewing the stakeholder engagement plan is too general; while stakeholder engagement is important, it doesn't directly address the functional failure of deliverables. Reviewing the quality management plan might be a subsequent step to understand quality processes, but the immediate need is to identify what specific requirement was missed. Reviewing the WBS would show the decomposition of work but not the functional performance of deliverables against requirements.