Which of the following is a requirement for entering Class C airspace?

Entering Class C airspace requires pilots to have a transponder with Mode C capability. Class C airspace is typically found around busy airports, and it is designed to protect aircraft operating within and near the airspace from collisions. The Mode C transponder allows Air Traffic Control (ATC) to track the aircraft's altitude and position, providing important data for maintaining separation between different aircraft in the crowded skies.

This requirement ensures that all aircraft entering Class C airspace are equipped with technology that allows for better surveillance by ATC. The surveillance information from Mode C transponders enhances safety by enabling ATC to provide traffic advisories and manage air traffic effectively in areas of high density.

While other aspects, such as filing a VFR flight plan or having prior communication with ATC, are generally recommended or required in various situations, they are not strict prerequisites for entering Class C airspace. Similarly, maintaining specific flight visibility might be essential for VFR flight but does not directly pertain to the requirements specifically associated with Class C airspace entry. Therefore, the transponder requirement is a vital part of ensuring safe and organized use of this controlled airspace.