What configuration can ensure constituents in a public sector organization's site cannot see each other?

The option to uncheck 'Site User Visibility' in sharing settings is the correct choice because it directly addresses the visibility of users within a public sector organization's site. When this setting is disabled, it restricts the ability of site users to see or interact with each other’s profiles and information. This is particularly important in public sector scenarios where privacy and confidentiality are paramount, allowing individual constituents to maintain their privacy while still accessing the resources and information needed.

The other configurations, while they may seem relevant, do not effectively achieve the intended result. Disabling user sharing in site settings might limit data sharing capabilities but does not specifically control visibility for all site users. Setting the Organization Wide Default for the User Object to “Public Read Only” would still allow users to see each other’s information, which contradicts the goal of preventing visibility among constituents. Lastly, removing access to the user object from the Permission Set affects specific permissions but does not fundamentally change the visibility settings across the site as a whole. Thus, unchecking 'Site User Visibility' is the most direct and effective way to ensure that constituents cannot see each other.