The correct option is PGP.

PGP is a suite of cryptographic standards for encrypting and signing data and email using public key cryptography. It is not an identity federation protocol and it does not provide mechanisms for issuing identity assertions or tokens for single sign on across domains. Federation protocols are designed to exchange authentication and authorization information between identity providers and service providers, while PGP is focused on message confidentiality and integrity.

OAuth is incorrect because it is a widely used authorization framework that issues access tokens for delegated access and it is commonly used in federated authentication scenarios when paired with identity layers.

OpenID is incorrect because the OpenID family of protocols provides identity federation and authentication. Modern OpenID Connect builds on OAuth to provide identity tokens and SSO. Note that older OpenID 2.0 has been largely superseded by OpenID Connect.

WS-Federation is incorrect because it is a web services federation protocol that enables single sign on and identity federation in enterprise environments and it is supported by many identity providers and platforms.

Full AWS Practitioner Certification Question