Which of the following in a federated environment is responsible for consuming authentication tokens?

The relying party, also known as the service provider, is the application or service that trusts the assertions made by the identity provider. It consumes the authentication token provided by the identity provider to grant access to its resources, essentially 'relying' on the identity provider for user authentication.

The identity provider is responsible for authenticating the user and issuing the authentication token, not consuming it.

A cloud services broker (CSB) acts as an intermediary, facilitating relationships between cloud consumers and providers, but does not directly consume authentication tokens for federated access.

An authentication provider is a general term for a service that authenticates users; in a federated context, it's typically the identity provider that issues tokens, while the relying party consumes them.