What is required to operate within Class C airspace?

To operate within Class C airspace, aircraft are required to establish two-way radio communication with the appropriate Air Traffic Control (ATC) facility and must be equipped with a transponder that has Mode C capability. This requirement ensures that ATC can identify and track all aircraft within that airspace, enhancing safety and effective air traffic management.

Class C airspace is typically located around busy airports where there is a significant volume of traffic. The requirement for two-way radio communication means that pilots must be able to communicate their intentions and receive instructions from ATC, which is essential for maintaining orderly traffic flow and avoiding collisions. The transponder with Mode C capability enables ATC to receive altitude information from the aircraft, further helping in maintaining safe vertical separation among aircraft.

The other choices, while they may pertain to certain operational requirements, do not encompass the complete set of necessary conditions for Class C airspace, making the option of two-way radio communication combined with a Mode C transponder the correct answer.