In Salesforce Knowledge, each article record includes visibility settings that determine where it can be accessed - for example, Internal App, Customer, Partner, or Public Knowledge Base.
To restrict specific articles to internal users only, set their visibility to "Visible in Internal App". This ensures they appear only to logged-in internal users (e.g., support reps), while remaining hidden from external users such as customers or partners.
Option A would make all Knowledge articles private, not just the confidential ones.
Option B disables standard sharing, which would affect system-wide access and is not recommended.
Referenced Salesforce Materials:
* Service Cloud Consultant Exam Guide - Knowledge Management Domain.
* Salesforce Help: "Control Article Visibility and Access."
* Salesforce Knowledge Implementation Guide - Visibility and Access Configuration.