Comprehensive and Detailed Explanation: Since the resource is critical and cannot be replaced, the project manager should coordinate with the other project lead to negotiate resource sharing. Collaboration between projects is the most immediate and effective approach before considering rescheduling or reassigning. * A assumes replacement is possible. * C is a reactive option without coordination. * D is planning-level, not execution-focused. * B is the proactive, stakeholder-aligned solution. References: * PMBOK Guide - Seventh Edition, Resource Management and Planning Domains * PMI Program Management Guidelines - Resource Conflict Resolution ############################################## Here are the reviewed and formatted responses to PMP Questions 1823-1826, with the correct answer, detailed explanations, and PMBOK Guide-aligned references: ##############################################