What characterizes a fully developed fire?

A fully developed fire is characterized by the fact that it has reached a state where it is consuming all available fuel and utilizing oxygen efficiently. In this stage, the fire has reached its peak intensity, producing maximum heat and flames. The fire's ability to continue growing is heavily dependent on the availability of additional fuel and oxygen. If either is restricted, the fire cannot grow larger; rather, it will stabilize at its current size or begin to diminish.

The other options do not accurately reflect the characteristics of a fully developed fire. For instance, a fire that burns out without any new fuel refers to a situation where the fire reaches a point of exhaustion, which is not typical of a fully developed scenario. Similarly, describing a fire that spreads slowly to objects would suggest a less intense situation, likely an incipient or growth phase. Lastly, noting a fire is still in the initial stage contradicts the very definition of what defines a fully developed fire, which is marked by vigorous burning and maximum spread.