Final answer:
To find the length of one side of the square, take the square root of the area which simplifies to 4xy^4.
Step-by-step explanation:
To find the length of one side of the square, we need to take the square root of the area. The area of the square is 16x^4y^8, so the length of one side is √(16x^4y^8). Simplifying this expression, we get 4xy^4. Therefore, the expression that could represent the length of one side of the square is B) 4xy^4.