Which of the following allows users to access connected system features through account federation?

MFA (Multi-Factor Authentication) requires more than one method of verification to grant access but does not inherently enable access to multiple systems with a single login via federation.

NAC (Network Access Control) restricts network access for endpoint devices based on security posture but does not facilitate federated access to system features.

Single Sign-On (SSO) is an authentication scheme that allows a user to log in with a single ID and password to gain access to multiple related yet independent software systems. Account federation, a key component of SSO, involves establishing trust between identity providers and service providers, allowing the user's identity to be authenticated once by an identity provider and then used across various connected services without re-entering credentials.

UAC (User Account Control) is a security feature in Windows that helps prevent unauthorized changes to the operating system by prompting for administrative approval, and it is unrelated to account federation or accessing multiple systems.