Final answer:
A Mode C transponder provides pressure altitude and requires Secondary Surveillance Radar (SSR) to operate.
Step-by-step explanation:
A Mode C transponder provides pressure altitude information. This altitude is based on the standard atmospheric pressure of 29.92 inches of mercury and it is the altitude displayed on the aircraft altimeter when it is set to this standard pressure setting. The pressure altitude is translated by the transponder from the raw data provided by the aircraft's pressure altitude encoder.
The type of radar required for a Mode C transponder is a Secondary Surveillance Radar (SSR). SSR is an advanced system that queries the transponder in the aircraft, which in turn responds to the interrogation with information such as altitude, squawk code, and potentially even aircraft identification.
The correct answer to the question would be: b) Pressure Altitude / SSR.