Write an Equation to Describe the Variation $r$ A) $r = k a$

Multiple Choice

Write an equation to describe the variation. Use k for the constant of proportionality.
-a varies directly as $r$

A) $r = k a$
B) $a = k r$
C) $r = \frac { k } { a }$
D) $a = \frac { k } { r }$