You need to monitor the availability of an Azure web app named App1 using a multi-step web test. Which feature in Azure Monitor should you use?

Azure Application Insights is the correct choice because it provides robust application performance monitoring (APM) capabilities, including multi-step web tests. These tests simulate user journeys through your web application, allowing you to monitor availability and performance from various locations. Azure Service Health focuses on the health of Azure services themselves, not your specific application. Diagnostic settings are used for collecting logs and metrics from Azure resources, but they don't offer multi-step web testing functionality. While metrics can show availability, they don't provide the detailed, scenario-based testing that a multi-step web test offers.