What action is a pilot permitted to take if they lose radio communications while operating under an ATC clearance?

When a pilot loses radio communications while operating under an Air Traffic Control (ATC) clearance, the appropriate action is to continue on the last assigned route and maintain altitude. This response is based on the principles outlined in aviation regulations, specifically those pertaining to lost communications procedures.

The rationale for maintaining the last assigned route and altitude comes from the need to ensure consistency and safety in communication. ATC issues clearances with specific routes and altitudes for a reason, often to manage air traffic and ensure safe separation between aircraft. By adhering to the last clearance, the pilot helps maintain predictable flight behavior that benefits both their own safety and that of other aircraft in the vicinity.

Continuing on the last assigned route means that the pilot is still operating within the structured system of air traffic management, potentially preventing conflicts with other aircraft. It is crucial for pilots to have knowledge of what to do in various communication failure scenarios, and this specific guidance minimizes confusion and enhances safety.

The other options imply actions that deviate from the established ATC clearance protocol, potentially leading to safety risks or regulatory violations. Thus, option B is the correct response in such situations.