The correct answer is B because the scenario requires disciplined compliance and quality governance rather than an immediate, informal, or purely administrative reaction. The selected response — B. Hold a retrospective on why the requirements were overlooked and update organizational process assets. — directly addresses the condition described in the question and keeps the project aligned with authorized objectives. PMBOK-aligned practice requires the project manager to verify mandatory requirements, analyze impact, and prevent uncontrolled delivery decisions that could create audit or acceptance exposure. This is especially important when project constraints, stakeholder expectations, quality expectations, delivery cadence, or business value may be affected. The competing options are weaker because they either bypass the accountable role, defer action without analysis, escalate before the project manager has prepared decision-quality information, or solve a symptom without correcting the underlying process issue. The selected answer also preserves transparency, ownership, and traceability, which are essential for sound project governance and effective delivery. PMBOK® Guide Eighth Edition topics: process, compliance and quality governance, stakeholder communication, impact analysis, governance, value delivery, and continuous improvement.