Which cloud is characterized by its flat bottom and domed top?

The cloud characterized by a flat bottom and a domed top is indeed the cumulus cloud. Cumulus clouds typically form in fair weather conditions and are known for their puffy, white appearance with a distinct, often flat base. As they develop, they can grow taller, leading to a dome-like shape at the top, resembling cotton balls in the sky.

Cumulonimbus clouds, while also having a towering structure, are more associated with severe weather, including thunderstorms, and do not possess the same flat bottom characteristic. Stratocumulus clouds have a more layered and patchy appearance without the pronounced dome, while nimbostratus clouds are thick and uniform, usually producing steady precipitation without the prominent top shape. Thus, the distinctive features of the cumulus cloud—its flat base and rounded top—make it the correct choice in this context.