Which of the following supports external user authentication in CyberArk?

The option indicating Vault Integrated External authentication is the most appropriate choice because CyberArk provides a feature specifically for integrating external authentication mechanisms to enhance security and streamline user access management. This feature allows organizations to use their existing identity management systems to verify the identity of users attempting to access the CyberArk vault.

By leveraging Vault Integrated External authentication, organizations can implement Single Sign-On (SSO) capabilities, utilizing methods such as SAML or OAuth. This integration not only simplifies user management but also strengthens security by centralizing the control of user credentials and access policies.

In contrast, while Active Directory and LDAP are indeed common authentication methods, they do not specifically represent the integrated solution that is tailored within CyberArk's infrastructure. Similarly, RADIUS is a protocol that can be used for remote user authentication; however, it doesn't cover the comprehensive capabilities offered by the Vault Integrated approach. Thus, the exclusive feature of Vault Integrated External authentication emphasizes its role in supporting seamless and secure user authentication processes within CyberArk's architecture.