To meet the monitoring requirements for App1, which service should you use?

Azure Application Insights is the correct choice because it is an Application Performance Management (APM) service designed specifically for monitoring live web applications. It provides comprehensive telemetry data, including request rates, response times, failure rates, dependencies, and traces, which are crucial for understanding application health and performance. Splunk is a powerful log management and analytics platform, but it's a third-party solution that requires more integration effort compared to the native Azure offering for APM. Azure Advisor provides personalized recommendations for optimizing Azure resources but doesn't offer real-time application monitoring. App Service logs provide basic diagnostic logs for Azure App Services but lack the deep application-level insights and performance monitoring capabilities of Application Insights.