When customers sign in to an Experience Cloud site with Facebook or LinkedIn credentials, Salesforce is consuming identity from those providers. In federation terms, that means Salesforce is the service provider and the social platforms are acting as the identity providers. This is a foundational identity concept and helps explain why the configuration happens through authentication providers in Salesforce. Salesforce is not issuing the social credential; it is trusting the identity assertion or token from the external provider and then creating or locating the user locally. Understanding that role assignment is important because it determines where trust is configured, where profile data originates, and how the registration handler fits into the login process. This is why option C is the best answer in Salesforce terms.