What is 'question answering' in Azure AI Language and what are its two main types?
Custom QA trains on your knowledge base; prebuilt QA queries a document provided in the request — both extract natural language answers.
Why this answer
Option B is correct because Azure AI Language's 'question answering' feature provides two distinct capabilities: Custom QA, where you train a model on your own documents (e.g., PDFs, FAQs) to answer questions from that knowledge base, and Prebuilt QA, which uses a document provided at query time to extract answers without prior training. This distinction is fundamental to how the service is deployed—either as a persistent, trained knowledge base or as an on-the-fly extraction from a user-supplied document.
Exam trap
The trap here is that candidates confuse the 'two main types' with operational characteristics (e.g., real-time vs. batch) or data format distinctions (structured vs. unstructured), rather than recognizing the official Azure classification based on whether the knowledge source is pre-trained (Custom) or provided at query time (Prebuilt).
How to eliminate wrong answers
Option A is wrong because 'question answering' in Azure AI Language does not involve multiple-choice question generation or open-ended answer scoring; it is a retrieval-based system that extracts answers from provided content, not a generative or scoring mechanism. Option C is wrong because Azure AI Language's question answering is not categorized by structured vs. unstructured data sources; both Custom and Prebuilt QA can handle unstructured text, and the service does not natively support structured database queries (that would be Azure Cognitive Search or SQL-based services). Option D is wrong because the two main types are not real-time vs. batch processing; both Custom and Prebuilt QA can operate in real-time or batch modes depending on the application, and the official classification is based on whether the knowledge source is pre-trained (Custom) or provided at query time (Prebuilt).