The correct answer is D because the scenario requires disciplined adaptive delivery rather than an immediate, informal, or purely administrative reaction. The selected response — D. Collaborate with the agile expert to implement a tailored strategy. — directly addresses the condition described in the question and keeps the project aligned with authorized objectives. PMBOK-aligned practice requires the project manager to protect the feedback loop, keep prioritization transparent, and route product decisions through the accountable role. 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: people, adaptive delivery, stakeholder communication, impact analysis, governance, value delivery, and continuous improvement.