Which of the following is considered a prohibited operation for UAS?

Operating a UAS at night without proper lighting is considered a prohibited operation due to safety regulations established by the FAA. For a UAS to be flown at night, it must be equipped with appropriate lighting that allows the pilot to maintain visual line of sight and to ensure the drone's position and orientation can be discerned. This is crucial for avoiding collisions with obstacles and other aircraft, as visibility is significantly reduced after dark. Without such lighting, the risks associated with night flying increase, making it a violation of regulations.

Other operations such as flying over populated areas, conducting search and rescue missions, and utilizing a UAS for agricultural purposes may have specific guidelines and requirements, but they are not categorically prohibited under the same circumstances as nighttime operations without proper lighting. Therefore, the requirement for adequate lighting stands out as a critical safety measure for night operations.