What is the fully developed stage in fire development characterized by?

The fully developed stage in fire development signifies a crucial phase where the fire has reached its peak intensity and is burning at its maximum rate. During this stage, the available combustible materials and the oxygen supply have reached appropriate levels to maintain and enhance combustion. The fire has typically spread throughout the entire involved area, consuming the available fuels. This stage is marked by high temperatures and intense heat release, resulting in significant fire behavior changes such as rapid spread and hazardous conditions.

Understanding the fully developed stage is essential for fire responders, as it indicates that the fire is at its most dangerous and stable point, necessitating strategic firefighting tactics to manage the situation effectively.

In contrast, the other options highlight different points in the fire's lifecycle: the beginning of combustion pertains to the initial stage, a decrease in oxygen supply suggests a later stage leading toward potential smoldering or extinguishment, and complete extinction signifies the end of the fire's lifecycle. Thus, the maximum rate of fire spread is a distinctive characteristic of the fully developed stage, making it the correct choice in this context.