Comprehensive and Detailed Explanation From Exact Extract:

The best practices guide for AgentForce and RAG emphasises that when using unstructured data and search indexes for grounded responses, you must consider privacy, security and data sensitivity. It mentions that search indexes should be curated, fields selected, and vectorised only where appropriate. Masking sensitive data and limiting index to non‑PII or aggregated forms is aligned to compliance and governance. Relying purely on prompt logic (option B) is unsafe; encrypting embeddings but still indexing raw PII (option C) still poses risk. Hence the correct and safe practice is option A.