The correct answer is Implement an SSO solution because SSO is the process that allows network users to provide their credentials just once to gain access to multiple applications and services. Implementing an SSO solution simplifies the user experience by requiring only one set of login credentials, reducing password fatigue and decreasing the chance of a security breach due to weak user credentials. On the other hand, SSH keys are primarily used for secure remote login from one computer to another and not for SSO across multiple web applications. Centralized user management is used to manage user accounts and permissions from a single location, which is not specific to the single authentication process required by SSO. Lastly, implementing PAM does not directly provide SSO capabilities, as PAM is used for implementing flexible authentication mechanisms for local system access.