What are characteristics of a moist, unstable air mass?

A moist, unstable air mass is characterized by its ability to rise quickly, leading to the formation of cumulus-type clouds, commonly referred to as cumuliform clouds. These clouds tend to indicate vertical development and are often associated with convective activity, which can result in showery precipitation. When the air is moist and unstable, it rises, cools, and condenses at higher altitudes, forming these clouds, which can produce showers or thunderstorms.

In contrast, the other characteristics mentioned in the other choices do not align with the behavior of a moist, unstable air mass. Poor visibility and smooth air are typically found in stable air masses where atmospheric motions are subdued. Stratiform clouds often develop in stable air conditions where there is minimal vertical motion, and they do not characterize instability. Clear skies and high temperatures may occur in dry and stable conditions, which is the opposite of the instability and moisture observed in a moist, unstable air mass.