A Responsibility Assignment Matrix (RAM) is the best tool for assigning and clarifying roles and responsibilities. A RAM maps project work (deliverables, work packages, or tasks) to people/roles and defines who is responsible/ accountable, and who provides input or needs to be informed (often implemented as a RACI chart). CompTIA Project+ lists RAM/RACI-style responsibility mapping under planning and resource management practices because it prevents ambiguity, reduces duplication, and supports accountability. () The distractors are not designed for role assignment. ERP is an enterprise resource planning system used to manage business processes; it can store resource data but isn't the PM artifact for defining responsibilities.
JAR is not a standard project management responsibility tool in this context. CCB (Change Control Board) governs change requests; it does not assign day-to-day delivery responsibilities.
Using a RAM early (initiation/planning) helps the PM establish clear ownership, streamline handoffs, and support effective communication planning. It also reduces the risk of "I thought someone else was doing that," which is a common execution failure mode when responsibilities are not explicitly documented. ()