The correct answer is B: Natural language processing. This is because natural language processing (NLP) is the AI workload designed to handle and analyze human language in text form. Key phrase extraction, a feature of Azure Cognitive Service for Language, is an example of NLP, and it identifies main concepts in text to help generate summaries. Other options such as anomaly detection, computer vision, and knowledge mining are not suitable for this task as they do not specifically deal with extracting key terms from text.