A systems administrator needs to integrate authentication with a partner so the employees of two companies can access the environment with control and management. Which of the following configuration

Single sign-on allows a user to authenticate once and access multiple applications, but it does not establish the inter-organizational identity trust needed between two separate companies.

Federation Services - such as Active Directory Federation Services (ADFS) or SAML 2.0 federation - creates a trust between two identity providers belonging to different organizations, allowing each company's users to present their home-organization credentials and receive access tokens valid in the partner environment. This is the correct solution because it enables controlled, managed cross-organizational authentication without requiring duplicate accounts. The administrator configures a relying-party trust and claims rules to govern exactly what access is granted.

Multifactor authentication adds a second verification factor to logins but does not create a trust relationship or enable cross-organizational identity federation.

Key management covers the lifecycle of cryptographic keys and certificates and does not address the authentication trust or identity federation between two organizations.