Product owners at Universal Containers want to ensure that all the requirements have test cases...

The correct selection is D. A requirements traceability matrix maps each approved requirement or acceptance criterion to one or more test cases and execution results. It is the artifact specifically designed to prove that UAT coverage is complete and that no requirement has been left without validation. From a testing perspective, the goal is deterministic evidence that the solution behaves correctly under the conditions that matter. Tests should isolate external dependencies, use controlled data, exercise positive and negative paths, and reproduce realistic volume or user behavior where required without making production the first place defects are discovered. The other options are weaker because they sacrifice isolation, realism, or repeatability and therefore make failures harder to reproduce and diagnose across environments. For this scenario, the decisive point is therefore the platform behavior represented by the selected option (D. Requirement traceability matrix). Applying that rule consistently keeps the implementation aligned with Salesforce-supported lifecycle practices and makes the resulting change easier to review, validate, and operate across environments.

Study Guide reference: Testing — Apex testing; test-data isolation; mocks; regression testing; performance/load testing; sandbox test strategy.