What action must be taken to ensure an aircraft is properly parked in a designated area?

Setting the parking brake is essential when parking an aircraft to ensure it remains stationary and does not move unintentionally. Activating the parking brake applies pressure to the aircraft's wheel brakes, which locks the wheels in place and prevents any rolling or drifting, especially on inclines or uneven surfaces. This is a critical safety measure to protect both the aircraft and personnel working around it, as it helps to prevent accidents or damage caused by movement.

While chocking the wheels is also an important step in aircraft parking, relying solely on wheel chocks may not provide sufficient security, particularly in varying environmental conditions. Activating tow status mode is related to preparations for towing an aircraft rather than securing it in place. Releasing the manual parking brake would defeat the purpose of securing the aircraft and is not a proper action for ensuring an aircraft is properly parked. Therefore, setting the parking brake is a necessary and effective measure for safely securing an aircraft in its designated area.