Final answer:
The side of a fire that is most threatened as a cold front passes is the side opposite the direction of the front's movement. The wind change associated with the front can escalate the fire towards new fuel sources and intensify its spread.
Step-by-step explanation:
As a cold front passes, the side of a fire that is threatened the most is the side opposite the direction of the front's movement.
This means that the correct answer is B) The side opposite the direction of the front's movement. When the front moves through an area, it can change the direction and speed of the wind, which in turn can push the fire towards new fuel sources. In addition, the wind associated with the front can cause the fire to burn more intensely by providing additional oxygen and removing the layers of cooler air that can act as a barrier to the fire's spread.