C: Organization information is stored in the Instance entity of the Discovery service. To see the kind of information contained in that entity, send an HTTP GET request to the service for one of your instances.
GET https://dev.{servername}/api/discovery/v9.0/Instances(UniqueName='myorg') In the above example, the discovery service is used to obtain the organization information of the instance with a unique name of "myorg".
Reference:
https://docs.microsoft.com/en-in/dynamics365/customerengagement/on-premises/developer/webapi/discover-url
https://docs.microsoft.com/en-us/powerapps/developer/common-data-service/webapi/samples/global-discovery-s