Comprehensive and Detailed Explanation From Exact AWS AI documents:

Retrieval Augmented Generation (RAG) enhances LLM responses by:

Retrieving relevant information from external knowledge sources

Injecting retrieved content into the prompt context

Reducing hallucinations and improving factual accuracy

AWS generative AI guidance describes RAG as a best practice when models must use up-to-date or domain-specific knowledge that is not embedded in the model weights.

Why the other options are incorrect:

RL (A) focuses on reward-based learning.

NLP (B) is a broad field, not a specific technique.

Transfer learning (D) adapts model weights but does not retrieve external data at inference time.

AWS AI document references:

Retrieval Augmented Generation on AWS

Improving LLM Accuracy with External Knowledge

Generative AI Architectures