The Salesforce role hierarchy, by default, grants managers access to records owned by their subordinates. The core requirement is to prevent this specific type of access for the feedback object. The most direct way to achieve this is by disabling the hierarchical access for that specific custom object. By unchecking 'Grant Access Using Hierarchies' in the Organization-Wide Defaults, an administrator ensures that a user's position in the role hierarchy does not automatically grant them access to records owned by users below them. This isolates record visibility strictly to the owner and those granted access through other sharing mechanisms, fulfilling the privacy requirement.

B. Define a criteria-based sharing rules.

Sharing rules are used to grant more access to records, not to restrict access that is already granted by the role hierarchy.

C. Set the default external access to private.

External access settings apply to external users (e.g., community or portal users), not internal employees like managers and their staff.

D. Configure an owner-based sharing rules.

Similar to criteria-based rules, owner-based sharing rules are designed to expand record access to additional users, not to prevent access.

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1. Salesforce Help, "Organization-Wide Sharing Defaults":

Section: "Grant Access Using Hierarchies"

Content: "For most objects, you can enable or disable access to records through your role hierarchy. For custom objects, you can deselect Grant Access Using Hierarchies if you want to prevent users from gaining access to data owned by other users in the same role or in roles below them in the role hierarchies." This directly validates that unchecking this option is the correct method to meet the requirement.

2. Trailhead, "Data Security" Module, "Control Access to Records" Unit:

Section: "Role Hierarchies"

Content: "The Grant Access Using Hierarchies option is enabled by default for all objects... You can change this setting for custom objects only... Disabling this setting for a custom object makes it so that managers in the role hierarchy don't get automatic access to their subordinates' records of that custom object type." This confirms that this setting is the specific control for hierarchical access on custom objects.

3. Salesforce Security Guide:

Chapter: "Controlling Access Using the Role Hierarchy"

Content: The guide explains that the role hierarchy provides vertical access to data. It also clarifies that for custom objects, this hierarchical grant can be disabled on the Organization-Wide Defaults page, which is a fundamental exception to the standard hierarchy behavior. This supports the choice of disabling the feature over using sharing rules, which only add permissions.