Q: Which of the following are protocols used for SSO?  

Correct option:
All the above options

Explanation:
All of the listed protocols are commonly used for Single Sign-On (SSO):

• OpenID Connect is a protocol that works on top of OAuth 2.0, allowing users to authenticate with an identity provider.
• SAML (Security Assertion Markup Language) is an XML-based protocol that allows secure exchange of authentication and authorization data between an identity provider and a service provider.
• Kerberos is a network authentication protocol that uses secret-key cryptography for authenticating users and services.
• OAuth is a token-based protocol primarily used for authorization but can also be used as part of SSO implementations.

Thus, all of these protocols can be used for implementing SSO.