Which service can you use to find underutilized or idle Azure virtual machines?

Azure Advisor is the correct answer because it provides personalized recommendations to optimize your Azure deployments for cost, performance, reliability, operational excellence, and security. Specifically, it identifies idle or underutilized resources, including virtual machines, and suggests actions to reduce costs. Azure Cost Management + Billing helps you understand your Azure spending and manage your budget, but it doesn't directly recommend specific resource optimizations like identifying underutilized VMs. Azure Reservations allow you to pre-purchase Azure services at a discounted rate, which is a cost-saving measure but not a tool for identifying underutilized resources. Azure Policy helps enforce organizational standards and assess compliance, but it doesn't analyze resource utilization for optimization recommendations.