[&] Every resource in your subscription is assigned an "owner" who is a point of contact for the resource.  All of the resources in any resource group are assigned to the same owner.  If a resource is moved from one resource group to another it will be associated with the owner of the target resource group. How can this be done with the least administrative effort?
- Create a policy that requires an "owner" tag with a value and apply the policy at the subscription level
- Create a policy that requires an "owner" tag with a value and apply the policy to every resource group
- Create a policy that assigns an owner tag to every resource.  Make the owner value a parameter and apply the policy to each resource group, specifying the parameter value for the resource group
- Assign an owner tag to each resource group -- Correct