What is the vertical extension of the core area of Class C airspace?

The correct choice reflects the altitude designation of Class C airspace, which extends from the surface up to 4,000 feet above ground level (AGL). Class C airspace typically surrounds busy airports, and the vertical limits are specifically structured to provide sufficient airspace above the airport's operational area to ensure a safe and organized flow of air traffic.

This structure is key for managing the complexities of air traffic in the vicinity of airports that handle significant amounts of commercial and general aviation operations. The designation of extending from surface to 4,000 AGL provides a buffer that supports both arriving and departing aircraft, accommodating the transition of flights into and out of this controlled airspace.

Other altitudes mentioned in the options do not accurately reflect the established limits for Class C airspace, and thus do not serve the same safety and operational purposes as the stated correct choice. Understanding these distinctions is crucial for pilots and those involved in air traffic control as it ensures compliance with regulatory standards and enhances safety in flight operations.