Which of the following definite integrals represents the volume of the solid whose base is the disk x2+y2≤16 and whose cross sections perpendicular to the x–axis are squares?
a) ∫−44216−x2dx
b) ∫−44(216−x2)2dx
c) ∫04(216−y2)2dy
d) ∫−44(16−x2)2dx