Clearance and obstruction lights are best described as:

• A. White and located on the ground
• B. Red and mounted on structures of various types, sizes and heights which could present a hazard to aircraft
• C. Green and used on taxiways
• D. Yellow and used on aircraft

Answer: (B)

Clearance and obstruction lights are red lights placed on tall or otherwise hazardous structures near an airport to warn pilots of obstacles in the airspace. They are mounted on structures of varying types, sizes, and heights that could pose a hazard to aircraft, helping pilots see and avoid them, especially at night or in poor visibility. They’re not located on the ground, and they aren’t green or yellow lights used on taxiways or aircraft. This red obstruction lighting is specifically about marking hazards, which is why it best matches the description.