Informal Argument for Volume of Sphere Practice Test

A class is discussing why the volume of a sphere of radius $r$ can be justified without calculus by comparing it to a cylinder of radius $r$ and height $2r$ with two congruent cones removed (each cone has base radius $r$ and height $r$). Which statement justifies the sphere’s volume formula?

In using Cavalieri's principle to find the volume of a sphere, a student sets up the comparison incorrectly and uses a cylinder of radius $$r$$ and height $$r$$ (instead of height $$2r$$) with one cone removed. At what height $$h$$ from the bottom would the cross-sectional areas first fail to match?