Your team needs to have a tool that provides a digital online (AZ-900)

Correct answer: C) Azure Al bot. Azure Machine Learning: This service is focused on building and deploying machine learning models, not specifically for creating digital online assistants with speech support.
Azure IoT Hub: This service is designed for connecting and managing internet of things (IoT) devices. While it can be used for some aspects of a digital assistant, it lacks the speech recognition and natural language processing capabilities needed for a full-fledged solution.
Azure Functions: This service allows you to build serverless functions that can be triggered by various events. While it could be used to build parts of a digital assistant, it would require additional tools and services for speech recognition and natural language processing.
Azure AI bot: This service is specifically designed for building and deploying intelligent bots that can interact with users through various channels, including voice. It provides out-of-the-box speech recognition and natural language processing capabilities, making it the ideal choice for this scenario.

Therefore, Azure AI bot is the most suitable service for your team's need to create a digital online assistant with speech support.