Which Azure service is best for creating a runbook to automate patching of virtual machines?

Azure Automation is the correct choice because it provides a cloud-based automation service specifically designed for process automation, configuration management, update management, and hybrid automation. Its runbook capabilities are ideal for scripting and orchestrating tasks like VM patching. Azure Functions is a serverless compute service for event-driven code execution, not primarily for orchestrating IT processes. Azure DevOps Pipelines are for continuous integration and continuous delivery (CI/CD) workflows, focusing on application deployment rather than IT operations automation. Azure CLI is a command-line interface for managing Azure resources, not an automation service itself.