If anything in the fourth line data block is not understood, what should the receiving controller do?

When a receiving controller encounters information in the fourth line data block that is not understood, the appropriate action is to inform the transferring controller. This choice emphasizes the importance of communication between controllers to ensure safe and efficient air traffic management. The fourth line in a flight plan typically contains specific information about the aircraft's intended route, departure, and arrival details, among others. If there are any ambiguities or uncertainties regarding this critical data, notifying the transferring controller allows for immediate clarification and rectification of any misunderstanding.

Effective communication is paramount in air traffic control because it helps to maintain situational awareness and uphold safety standards. By reaching out to the transferring controller, the receiving controller can confirm details or receive corrections, which helps prevent potential miscommunications that could affect the flight's trajectory or coordination with other air traffic.

The other possible actions do not foster the necessary collaborative communication needed in these situations. Revising the entire flight plan might be inappropriate without first clarifying the specific concerns. Assuming all information is correct poses a risk, as it can lead to errors in flight management. Contacting the supervisor for clarification may be unnecessary and could delay effective resolution, particularly when the transferring controller is best positioned to address the issues directly.