Which service can automatically send an alert if an administrator stops an Azure virtual machine?

Azure Monitor is the correct answer because it provides comprehensive monitoring of Azure resources, including virtual machines. It collects metrics and logs, allowing you to create alert rules based on specific events or performance thresholds. In this scenario, an alert rule can be configured to trigger when a virtual machine's status changes to "stopped" by an administrator, notifying you of the action. Azure Advisor provides recommendations for optimizing Azure resources but doesn't send real-time alerts for operational events. Azure Service Health informs you about Azure service outages and planned maintenance, not individual resource actions. Azure Network Watcher helps monitor and diagnose network-related issues, not administrative actions on virtual machines.