Which type of aerodrome has an operational air traffic control unit?

A controlled aerodrome is characterized by the presence of an operational air traffic control (ATC) unit. This setup is vital for managing air traffic safely and efficiently, particularly in areas with high traffic volume. The ATC unit provides communication and coordination services to pilots, ensuring that all aircraft are aware of each other's positions and intentions, thus facilitating safe takeoffs, landings, and navigation within controlled airspace.

In contrast, uncontrolled aerodromes lack an ATC unit, meaning pilots are responsible for their own navigation and separation from other aircraft. Private aerodromes may also be uncontrolled and usually cater to specific individuals or entities without the need for ATC services. General purpose aerodromes can vary in terms of operational control; therefore, they may or may not have an ATC unit based on their usage and traffic level. Thus, the defining feature of a controlled aerodrome is its operational ATC unit, making it the correct answer.