Final answer:
A Finger is a long narrow strip of fire that extends from the main fire, caused by variations in landscape or winds.
Step-by-step explanation:
The answer to the question which feature is a long narrow strip of fire extending from the main fire is Finger. When describing wildfires, the term 'finger' is used to refer to the projection of fire that extends from the main body of the fire, resembling a finger in shape.
This can happen due to variations in the landscape, wind patterns, or the availability of fuel, causing the fire to extend in a narrow strip. Unlike the head of the fire, which is the most rapidly spreading part, or the flank, which refers to the sides of the fire, a finger is typically a smaller extension of the fire.