Which of the following is a category of U.S. airspace?

The correct choice is controlled airspace. This category of airspace is regulated by the Federal Aviation Administration (FAA) and is subject to specific air traffic control (ATC) procedures. Controlled airspace is defined to ensure safe and efficient movement of aircraft, allowing ATC to provide oversight and management when necessary. It typically includes various classes of airspace, such as Class A, B, C, D, and E, each with its own rules regarding flight operations, pilot qualifications, and equipment requirements.

Understanding controlled airspace is essential for pilots because it dictates how and when they must communicate with ATC, which is crucial for maintaining safety and preventing airspace conflicts. Pilots must be aware of the boundaries and operational requirements of controlled airspace to comply with aviation regulations and ensure safe flight procedures.