Explanation/Reference: https://www.businessanalystlearnings.com/blog/2015/10/21/the-role-of-business-analysts-in-user- acceptance-test-sessions-how-to-identify-test-cases

Explanation
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.

The business analyst should determine if the defect is in the solution developed, in the original requirement, or in the test case. This criterion will help the business analyst to identify the root cause of the defect, and to decide the appropriate response to the defective test result. Depending on the source of the defect, the business analyst may need to revise the requirement, update the test case, or request a change to the solution. The business analyst should also communicate the defect and the response to the relevant stakeholders, and document the discrepancy report accordingly. References: PMI Professional in Business Analysis (PMI-PBA)Examination Content Outline1, page 25; Business Analysis for Practitioners: A Practice Guide2, page 140.