What does a transponder do?

A transponder plays a crucial role in aviation communication by sending information about an aircraft's identity, altitude, and position to Air Traffic Control (ATC) radar systems. When an aircraft is equipped with a transponder, it responds to radar signals from ATC by transmitting these important details. This allows ATC to track the aircraft's movements accurately and ensures safe separation from other aircraft in busy airspaces. The transponder's ability to relay this information enhances situational awareness for both pilots and air traffic controllers, significantly improving overall flight safety.

The other choices, while they address functions relevant to aviation, do not accurately describe the primary purpose of a transponder. Reducing fuel consumption is related to aircraft design and operational efficiencies rather than transponder functionality, monitoring temperature and pressure pertains to the aircraft's environmental and system management, and navigation using GPS data is handled by different onboard systems, not by the transponder itself.