Which Azure service is used to monitor and manage resource usage and compliance across an Azure subscription?

The correct choice for monitoring and managing resource usage and compliance across an Azure subscription is Azure Policy. This service allows organizations to create, assign, and manage policies that enforce specific rules and effects over their Azure resources. Azure Policy ensures resources are compliant with organizational standards and service level agreements by preventing the creation of non-compliant resources and evaluating existing resources for compliance.

Using Azure Policy, you can govern resource configurations, enforce tagging requirements, and maintain compliance with regulatory requirements by auditing resource states. It provides a way to enforce the compliance policies consistently across multiple Azure resources and subscriptions, ensuring that the resources adhere to the defined corporate governance and compliance policies.

While Azure Monitor is focused on collecting and analyzing telemetry data from your resources to provide insights and performance monitoring, it does not enforce governance regarding resource configuration. Azure Security Center enhances security management and threat protection but does not primarily focus on the compliance and governance aspect across resource usage. Azure Resource Manager is primarily a resource management tool that allows you to deploy, manage, and organize Azure resources but does not provide built-in compliance policies or monitoring in the same way that Azure Policy does.