Which type of cloud typically signifies stable atmospheric conditions?

Stratus clouds are indicative of stable atmospheric conditions primarily due to their formation process and characteristics. They typically occur when the air is stable, meaning there is little vertical movement within the atmosphere. Stratus clouds form in layers, creating a uniform gray overcast that can lead to steady light precipitation, but they do not generally produce significant turbulence or severe weather.

In contrast, other cloud types point to instability. Cumulus clouds, for example, are often associated with rising air and can develop into cumulonimbus clouds, which are indicative of unstable conditions-likely leading to thunderstorms. Nimbostratus clouds, while also capable of producing precipitation, typically form in conditions of sustained moisture and can suggest some degree of instability, though they are more stable than cumulonimbus clouds.

Overall, stratus clouds strongly correlate with a stable atmosphere, making them the correct answer in this context.