When an object's Organization-Wide Default (OWD) is set to Private, the "Record Sharing" engine must be used to grant additional access.
* Sharing Rules:These allow the administrator to grant lateral access to records based on criteria or ownership (e.g., share all "Large Deals" with the "Strategic Sales" group).
* Role Hierarchy: This standard feature automatically grants vertical access, ensuring that managers and users higher in the hierarchy can see and edit records owned by their subordinates.
Profiles (Option D) control what actions a user can perform (Create, Read, Edit) but do not grant access to specific records that the user does not own in a Private model. A Sharing Set (Option B) is a specific feature used for Experience Cloud (Community) users to grant them access to records related to their account and is not used for standard internal sales users.