Which clouds are classified as high clouds?

High clouds are defined as those that form at altitudes above approximately 20,000 feet. They are typically composed primarily of ice crystals due to the cold temperatures at such elevations. The classification of high clouds includes cirrus, cirrocumulus, and cirrostratus.

Cirrus clouds are thin, wispy clouds that often appear white and are usually associated with fair weather, although they can indicate that a change in the weather is coming. Cirrocumulus clouds are small, white patches of clouds often arranged in rows at high altitudes, giving a textured appearance to the sky. Cirrostratus clouds are thin, ice-crystal clouds that cover the sky and can create a halo effect around the sun or moon.

The other options either include cloud types that form at lower altitudes, such as stratus and cumulus clouds, or do not accurately represent the types of high clouds recognized in meteorology. Therefore, the most accurate grouping of high cloud types is the one that includes cirrus, cirrocumulus, and cirrostratus, affirming that option is the correct choice.