A requirements traceability matrix is a tool that links the requirements to their sources, objectives, and deliverables. It helps to track the status, changes, and verification of each requirement throughout the project life cycle. If the requirements traceability matrix was not updated with the change, it could result in a key requirement being missed or overlooked in the implementation. The other options are not likely to cause this problem. The requirements management plan is a document that describes how the requirements will be elicited, analyzed, documented, validated, and managed. The scope management plan is a document that describes how the project scope will be defined, controlled, and verified. The schedule management plan is a document that describes how the project schedule will be developed, monitored, and controlled. References: PMI-PBA® Examination Content Outline, page 13; PMI-PBA® Reference List, page 1, BABOK® Guide v3, page 39; 6.