The Circumference, In $\mathrm{cm}$ , of a Circle Whose Radius Is $r \mathrm{~cm}$

The circumference, in $\mathrm{cm}$ , of a circle whose radius is $r \mathrm{~cm}$ is given by $C=2 \pi r$ . If $C=f(r)$ , evaluate and interpret $f^{-1}(14 \pi)$ .

A) $28 \pi^{2}$ , the circumference of a circle with radius $14 \pi$ .
B) $28 \pi^{2}$ , the radius of a circle with circumference $14 \pi$ .
C) 7 , the circumference of a circle with radius $14 \pi$ .
D) 7 , the radius of a circle with circumference $14 \pi$ .