In Aura components, Salesforce provides specific interfaces that "inject" context into the component automatically. The developer is already using force:hasRecordId, which automatically populates a recordId attribute with the ID of the current record.

To get the API Name of the sObject (e.g., "Account" or "Contact") without writing Apex code or requiring manual configuration in the App Builder, the developer should implement force:hasSObjectName (Option D). When this interface is added to the implements attribute, the framework automatically provides an attribute named sObjectName to the component.

This is the most efficient solution because:

It is purely declarative and handled by the Lightning framework.

It requires zero Apex code, meaning there is no need for additional unit tests or code coverage (satisfying the requirement "without requiring additional test coverage").

It makes the component truly reusable; you can drop it on an Account page, a Contact page, or any custom object page, and it will immediately know which object it is currently displaying.

Options A and B require manual configuration or hardcoding, which reduces reusability. Option C requires an Apex call, which adds complexity and necessitates writing test classes for coverage.