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

Multiple Choice

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 $f(r+6)$ .

A) $2 \pi r+6$ , the circumference of a circle of radius $r+6$ .
B) $2 \pi r+6,6$ more than the circumference of a circle of radius $r$ .
C) $2 \pi r+12 \pi$ , the circumference of a circle of radius $r+6$ .
D) $2 \pi r+12,12$ more than the circumference of a circle of radius $r$ .