What information does Mode C supply to ATC?

Mode C transponders play a vital role in aviation communication by providing critical information to Air Traffic Control (ATC). Specifically, Mode C transmits both position and altitude information from the aircraft. The altitude data is particularly important for maintaining safe vertical separation between aircraft, whereas the position information helps ATC track the aircraft's location on radar screens.

In the context of air traffic management, this information is crucial as it allows controllers to ensure safe spacing between various aircraft, coordinate clearances, and manage traffic effectively in controlled airspace. Understanding an aircraft's altitude aids in avoiding potential collisions and enhances overall flight safety.

The other choices do not accurately represent the primary function of Mode C. While speed and trajectory can be inferred or calculated in some scenarios, they are not directly provided by Mode C. Similarly, maneuvering patterns and flight time estimates are not data points transmitted by Mode C transponders, as these would require additional information and systems not encompassed by the basic Mode C function.