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.

Protected custom metadata types in managed packages provide a secure way to store sensitive information like encryption keys. When packaged as part of a managed package, the metadata records are shielded from access by users, even those with View Setup and Configuration permissions.
* Option A: Custom metadata types without protection do not secure the key from users with View Setup permission.
* Option B: Unlocked packages do not provide the same level of protection as managed packages.
* Option C (Correct): A protected custom metadata type in a managed package ensures the encryption key is securely stored and cannot be accessed by users.
References:
* Custom Metadata Types