In what situation are cumuliform clouds most likely formed?

Cumuliform clouds are primarily formed under conditions where warm air is rising. This is because these clouds develop when moist air is buoyant and ascends, allowing it to cool at higher altitudes. As the warm air rises, it expands and cools, leading to condensation of moisture in the air, which then forms these characteristic fluffy clouds with a distinct vertical development.

This process is often associated with unstable atmospheric conditions, which promote the upward movement of air. Consequently, the formation of cumuliform clouds is a direct result of rising warm air, making it the correct answer in this context. Other scenarios, such as stable weather conditions or consistently low temperatures, are less conducive to the development of these clouds, as they do not typically support the rising motion necessary for their formation.