Your team needs to have a tool that can use past trainings to provide (AZ-900)

Correct answer: A) Azure Machine Learning.
The best service for your team's need to use past trainings to provide predictions of very high probability is Azure Machine Learning.
Here's why:
Azure Machine Learning: This service is specifically designed for building and deploying machine learning models, which are trained on past data to make predictions. It offers a variety of tools and features for training, managing, and deploying machine learning models, including algorithms optimized for making high-probability predictions.
Azure IoT Hub: While this service can be used to collect and store data that could be used for training machine learning models, it doesn't have the capabilities to train and deploy such models itself.
Azure AI bot: This service is primarily focused on building intelligent bots for interacting with users. While it can leverage machine learning models for certain functionalities, it's not specifically designed for high-probability predictions.
Azure Functions: This service is designed for running serverless functions, which can be used to invoke machine learning models deployed elsewhere. However, it doesn't offer the same level of comprehensive tools and features for managing and optimizing machine learning models as Azure Machine Learning.

Therefore, based on its focus on building and deploying machine learning models, Azure Machine Learning is the most appropriate service for your team's need to make high-probability predictions based on past trainings.