What type of cloud formation signifies the mature phase of a thunderstorm?

The mature phase of a thunderstorm is characterized by the presence of cumulonimbus clouds. These clouds are towering and often have a well-defined anvil-shaped top that indicates strong updrafts and the extensive vertical development typical of thunderstorms. Cumulonimbus clouds are associated with severe weather phenomena, including heavy rainfall, lightning, hail, and even tornadoes.

During the life cycle of a thunderstorm, the mature phase is when the storm reaches its peak intensity, and the presence of cumulonimbus clouds signifies this. The updrafts support the formation and sustenance of these clouds, leading to various storm-related phenomena. Other types of clouds, such as stratus, nimbostratus, and cirrus, do not exhibit the characteristics associated with the mature phase of a thunderstorm, which is why they are not the correct choice. Stratus clouds are typically flat and layered, nimbostratus clouds bring continuous precipitation but lack the severe dynamics of thunderstorms, and cirrus clouds are high, thin clouds that do not indicate storm activity.