Answer: Option 'C' is correct.
Step-by-step explanation:
Since we have given that
Area of triangle LMN = 18 ft²
Area of triangle FGH = 24 ft²
Since Δ LMN and ΔFGH is equivalent triangles.
As we know the theorem which states that ratio of areas of equivalent triangles is equal to square of ratio of corresponding sides.
So, it becomes,

Hence, Option 'C' is correct.