Informal Arguments for Circle/Solid Formulas Practice Test

Using Cavalieri's principle to compare the volumes of a cone and a pyramid with the same base area and height, which statement best explains why they have the same volume formula $$V = \frac{1}{3}Bh$$?

The circumference formula $$C = 2\pi r$$ can be justified by inscribing regular polygons in a circle. If $$P_n$$ represents the perimeter of a regular $$n$$-sided polygon inscribed in a circle of radius $$r$$, which expression correctly represents the limiting argument?