Files uploaded to a user's private library in Salesforce Files Home are strictly private and visible only to the user who uploaded them. Even users with elevated permissions, such as those with "View All Data" access, or users higher in the Role Hierarchy, cannot view these files. This ensures the utmost privacy for files stored in a private library.
* Option A: Role Hierarchy does not affect access to files stored in a private library.
* Option B: "View All Data" does not grant access to files in private libraries.
* Option C (Correct): Only the user who uploaded the file can view it in their private library.
References:
* Files Home Overview
* File Privacy and Sharing

Explanation
Using a trigger on Case to lookup and share to the manager of an Assigned Agent custom field using Apex Managed Sharing would allow the HR representative to control the visibility of the case based on the subject of the complaint. Criteria-based sharing rules cannot be used to exclude a specific user from seeing a record.
Changing the owner of the case would affect other aspects of data visibility and security.

Explanation
Enterprise Territory Management is a feature that allows you to assign accounts to territories based on criteria such as geography, industry, revenue, etc. With Enterprise Territory Management, you can1:
Use the Metadata API to create, update, and delete territory models, territories, and account assignments.
Integrate with Collaborative Forecasting to forecast sales revenue by territory.
Assign opportunities to territories based on the account assignment or other criteria.