Final answer:
To maximize the volume of an open box with height h and square base side of x, the formula is V = x²h.
Step-by-step explanation:
To maximize the volume of an open box with height h and square base side of x, we need to consider the formula for the volume of a rectangular prism which is V = lwh, where l is the length, w is the width, and h is the height.
In this case, the length and width are both x (since it is a square base), and the height is h. So the formula becomes V = x * x * h = x²h.
Therefore, the correct answer is C) V = x²h.