API Management helps organizations publish APIs to external, partner, and internal developers to unlock the potential of their data and services. You can secure API Management using the OAuth 2.0 client credentials flow. Incorrect Answers: A: Azure Active Directory B2B uses guest users. B: Azure Front Door is an Application Delivery Network (ADN) as a service, offering various layer 7 load-balancing capabilities for your applications. Azure Front Door supports HTTP, HTTPS and HTTP/2. Applications can be authorized through OAuth 2.0. D: Application Proxy is a feature of Azure AD that enables users to access on-premises web applications from a remote client. Application Proxy includes both the Application Proxy service which runs in the cloud, and the Application Proxy connector which runs on an on-premises server. Application Proxy works with: Web applications that use Integrated Windows Authentication for authentication Web applications that use form-based or header-based access Reference: https://docs.microsoft.com/en-us/azure/api-management/api-management-key-concepts