Which of the following describes Controlled Airspace?

Controlled airspace is defined as airspace within which air traffic control (ATC) services are provided to aircraft. This typically requires pilots to obtain ATC permission before entering that airspace. The need for ATC clearance helps ensure safe and efficient air traffic management, particularly in areas where there is significant air traffic or potential conflicts among aircraft.

In controlled airspace, air traffic controllers manage the flow of air traffic, providing instructions and services such as traffic advisories, weather updates, and guidance on navigation. This structured oversight is crucial for maintaining safety in busy airspace, particularly near airports where many aircraft may be operating simultaneously.

The other options refer to different types of airspace or scenarios that do not align with the definition of controlled airspace, where the primary characteristic is the necessity of ATC approval for entry. For instance, uncontrolled airspace does not have the same restrictions and allows pilots to operate without seeking validation from ATC.