What is the minimum operational equipment required for a student pilot in Class C airspace?

For a student pilot operating in Class C airspace, the minimum operational equipment required includes a transponder with Mode C capability or better. Class C airspace is characterized by its radar services for both IFR and VFR traffic, and the use of a Mode C transponder is essential for air traffic control to identify and track aircraft within this airspace. The transponder provides real-time altitude reporting and improves situational awareness for both the pilot and ATC.

In contrast, while a GPS navigation system may be useful for navigation, it is not a required piece of equipment for student pilots in Class C airspace. Similarly, an external lighting system, while necessary for operating under certain conditions, is not specifically mentioned as a requirement for entry into Class C airspace. Automatic dependent surveillance (ADS) is also not mandated for student pilots, although it can enhance traffic awareness and safety. Thus, the requirement for a transponder is the key reason it is considered the correct answer.