You design the secure integration between the Power Apps app and the on-premises system. The system is not accessible from the internet and has several REST endpoints. 
What service would you use in your design?

Answer options:

A.Azure Function
B.VPN
C.Azure Logic App
D.Azure Relay
E.Azure Event Hubs

Correct Answers: D 
Azure provides a Relay service for a secure connection to the services running on a corporate network without intrusive network changes or opening the firewall port. You can use the Azure Relay to connect the Power Platform solutions with the on-premises services. The on-premises service connects to the relay using an outbound port and creates a bi-directional socket with a dedicated address. The Power Apps app can make an HTTP call to the Relay service, and the service transfers a call to the on-premises listener. The app does not need to know the location of the on-premises service. Azure Relay establishes the connection between the app and on-premises service, and both parties can exchange messages with each other.
Option A is incorrect because the Azure Function is helpful for small units of work and helps to offload the logic operations from the Dataverse application host. But the Azure Function does not provide a secure connection between the Power Apps app and the on-premises system.
Option B is incorrect because VPN integration has a more demanding and network intrusive setup than Azure Relay.
Option C is incorrect because the Azure Logic Apps does not secure a connection between the Power Apps app and the on-premises system.
Option E is incorrect because the Azure Event Hub is a real-time data ingestion service that can process millions of events per second and deliver them to subscribers. But it does not provide a secure connection between the Power Apps app and the on-premises system.
For more information about the Power Platform and Azure Relay integration, please visit the below URLs: 

https://docs.microsoft.com/en-us/learn/modules/integrations/4-outbound
https://docs.microsoft.com/en-us/azure/azure-relay/relay-what-is-it
https://docs.microsoft.com/en-us/azure/azure-relay/relay-hybrid-connections-http-requests-dotnet-get-started