The correct answer is C because the troubleshooting need is retrieval-source traceability, not general data modeling or final LLM response writing. In Data 360 retrieval, the retriever searches a configured search index and returns relevant content to ground the prompt. If multiple sources feed the index, source metadata such as document type, author, origin, or content category can be used to filter or interpret retrieved chunks. Option A is too broad because harmonization maps source data into model structures, but it does not directly explain which grounding chunk produced a conflicting answer. Option B is wrong because the LLM should not be trusted to invent or automatically append source tags during synthesis. The retriever layer is where relevant indexed content is searched, filtered, ranked, and returned.