According to the Microsoft Azure AI Fundamentals (AI-900) Official Study Guide and the Microsoft Learn module “Explore conversational AI in Microsoft Azure,” conversational bots are AI applications that can understand and respond to natural language inputs through text or speech. Building such a bot typically involves two key Azure services:

Azure Bot Service (Option B):This service provides the framework and infrastructure needed to create, test, and deploy intelligent chatbots that interact with users across multiple channels (webchat, Teams, email, etc.). It handles conversation flow, integration, and user message management.

Azure Language Service (Option A):This service powers the natural language understanding (NLU) capability of the bot. It enables the bot to interpret user input, extract intent, and query a knowledge base using Question Answering (formerly QnA Maker). This allows the bot to respond intelligently to user questions by finding the most relevant answers.

The other options are incorrect:

C. Form Recognizer is used for extracting structured data from documents like invoices or forms.

D. Anomaly Detector is used for identifying unusual patterns in time-series data.

Hence, to build a bot that understands and answers user questions in natural language, the solution must combine Azure Bot Service for conversation management and Azure Language Service for knowledge-based question answering and natural language understanding.