How Do We Know the Nature of the Brown Ovals

How do we know the nature of the brown ovals in Jupiter's atmosphere?

A) They glow brightly in infrared, thus we know they are warm, high-altitude clouds.
B) They glow brightly in infrared, thus we know they are holes in the atmosphere that allow the escape of infrared from warmer, deeper layers.
C) The brown color matches other features at that level, so we know they form a continuous part of that atmospheric layer.
D) They glow dimly in infrared, thus we know they are actually at higher, colder levels in the atmosphere.