Which of the following is NOT a type of high cloud?

Stratus clouds are typically classified as low clouds rather than high clouds. High clouds generally include those that form above 20,000 feet, such as cirrus, cirrostratus, and cirrocumulus. These high-altitude clouds are characterized by their thin, wispy appearances and are composed of ice crystals due to the cooler temperatures at such heights. In contrast, stratus clouds are found at lower altitudes, usually around 6,500 to 20,000 feet, and appear as uniform grayish sheets that cover the sky, often bringing overcast conditions but not the same characteristics associated with high cloud types. Thus, stratus is the type that does not belong in the high cloud category.