Solving this problem is pretty straight forward. All we have to do is to find for the measure of one side since the shape is a cube so the formula for volume is:
V = s^3
where V is volume = 64 m^3, s is the measure of one side
64 m^3 = s^3
s = cuberoot (64 m^3)
s = 4 m
Therefore the size of the pictures are:
C. 4 x 4