Which cloud type is described as having a gray or black color with a large amount of moisture?

The cloud type that is characterized by a gray or black appearance and a significant moisture content is nimbostratus. These clouds are thick, uniform, and typically cover the sky, leading to a dim, overcast condition. When light passes through these clouds, they can appear dark, indicating their ability to produce steady and prolonged precipitation, often in the form of rain or snow.

Nimbostratus clouds are associated with extensive vertical development, which allows them to hold substantial amounts of moisture. This moisture is released over a widespread area, resulting in consistent, steady rainfall. Their presence is often a precursor to strong weather systems, making them significant for aviation weather forecasting and planning.

In contrast, other cloud types mentioned do not share these characteristics. Cumulus clouds are typically puffy, white clouds that indicate fair weather and are less dense. Altostratus clouds can bring light precipitation but do not usually appear as dark or carry as much moisture as nimbostratus clouds do. Stratocumulus clouds often have a more scattered, lumpy appearance and usually do not result in significant rainfall, making nimbostratus the definitive choice for the described conditions.