Explanation
A change in the requirement is a situation where the requirement is different from what was originally agreed upon by the stakeholders. This can happen due to various reasons, such as changing business needs, stakeholder feedback, regulatory changes, or technical constraints. To assess the change, the BA needs to conduct an impact analysis using traceability, which is a technique that involves identifying and documenting the relationships among requirements, stakeholders, solution components, and other artifacts. Traceability can help the BA to determine the scope, cost, schedule, quality, and risk implications of the change, and to communicate them to the relevant stakeholders for approval or rejection. The other options are not the best actions for assessing the change, as they are more suitable for different purposes, such as closing a defect that is not a defect, evaluating the potential threats and opportunities of the change, or finding the underlying cause of the defect. References: CBAP Handbook, CBAP Study Guide, BABOK Guide