What must be done when calling the service NS endpoint?

 The correct answer is B because when calling the serviceNS endpoint, you must specify the user and app context in the URI. The serviceNS endpoint is a REST endpoint that allows you to access the Splunk service for a specific namespace. The namespace is a combination of the user and the app context, which determine the scope and visibility of the knowledge objects in Splunk. The serviceNS endpoint requires you to specify the user and app context in the URI, such as /servicesNS/{user}/{app}. Option A is incorrect because you do not need to authenticate with an admin user, but rather with the user of the required context. Option C is incorrect because you do not need to authenticate with the user of the required context, but rather with any valid user. Option D is incorrect because you do not need to pass the user and app context in the request payload, but rather in the URI. You can find more information about the serviceNS endpoint and the namespace in the Splunk REST API Reference Manual.