The figure here is a ring with a thickness shown in black. If the radius to the outside edge of the ring is r and the thickness of the ring is t, then which of the following expressions best describes the area of the ring's thickness?

`pi(r-t)^2`

`pi(r^2 - t^2)`

`2pi(r-2t)`

`pir(2r-t)`

`pit(2r-t)`