The volume of a cone is given by the formula
$\qquad V=\dfrac13 \pi r^2h$
where $~r~$ is the radius of the circular base and $~h~$ is the height of the cone.
In the diagram, $~A=(0,h)\,$, $~B=(r,h)\,$, and $~C=(0,0)\,$. If we take $~\triangle ABC~$ and rotate the region about the $~y$-axis, the resulting solid is a cone.
$\qquad$
Using the diagram, which of the following integral expressions would be used to prove that the volume is indeed $~\dfrac 13 \pi r^2h\,$?
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