Firebrands can contribute to the spread of fire by:

Firebrands, also known as embers, are burning or smoldering pieces of material that can be carried by wind and can ignite new fires in areas not directly involved in the main fire. When firebrands land on combustible materials, such as dry leaves, grass, or wood, they can easily cause these materials to ignite, leading to the spread of fire beyond the original area.

This process is significant because it can create spot fires ahead of the main fire front, complicating fire suppression efforts and making fire behavior unpredictable. Understanding the role of firebrands in fire behavior helps firefighters anticipate potential fire spread and develop effective strategies for containment.

The other choices do not accurately represent the role of firebrands in fire spread. For example, creating a barrier, irradiating the ground, or cooling the fire area do not align with the function of firebrands, which is primarily to initiate new ignitions rather than to act as a cooling or containing mechanism.