Mode C of a transponder transmits information that includes:

Mode C of a transponder transmits both the squawk code and the aircraft's altitude. This capability is essential for air traffic control, as it allows controllers to identify and monitor the aircraft's position and altitude in real-time on their radar screens. The squawk code is a four-digit code assigned to the aircraft that avoids confusion with other aircraft in the same airspace. The altitude information makes it possible for controllers to ensure safe vertical separation between aircraft.

While the other options mention factors like location coordinates, speed, and airspeed, these are not part of the data transmitted by Mode C. Mode C specifically emphasizes the squawk code and altitude, which are vital for maintaining safety and efficient airspace management. Understanding this distinction is crucial for recognizing how transponder modes function in aviation operations.