Comprehensive and Detailed Explanation: The project manager must educate stakeholders on the value of reserves for unknown risks. It's essential to obtain buy-in, especially when the sponsor disagrees. Open communication and justification based on risk management principles are part of best practices. * A is too confrontational. * C bypasses the sponsor, which is inappropriate. * D gives in without resolving the risk concern. * B is the balanced, PMI-aligned approach. References: * PMBOK Guide - Seventh Edition, Planning and Risk Performance Domains * PMI Risk Management Professional (PMI-RMP)® Practices ##############################################