Use the Public Complaint and Case objects. This is the lowest-customization answer that still satisfies the business, security, and lifecycle requirements.

The Core Concept Explained: Experience Cloud design is driven by persona, authentication, scale, and sharing. The wrong template or license can create unnecessary cost, weak security, or excessive customization.

Step-by-Step Technical Analysis: Begin with the external persona, authentication requirement, and transaction volume. Select the Experience Cloud license or template that matches that access pattern, then configure sharing sets, external OWD, site visibility, and page access. Finish by testing the experience as anonymous, authenticated, and internal users. Use the Public Complaint object for the external concern and Case for the internal follow-up work. For exam preparation, validate the answer by tracing the record lifecycle, the user persona, and the automation owner from intake through reporting.

Why the Incorrect Options Are Wrong: A uses the wrong packaged object or module boundary for this scenario. C adds a custom build path and increases lifecycle, security, and upgrade effort when a packaged or declarative capability already supports the requirement.