Chapter 8 - Complex Numbers, Polar Equations, and Parametric Equations - Section 8.5 Polar Equations and Graphs - 8.5 Exercises - Page 389: 41

$r=3$ We can see that this equation matches with option (C)

$r=3$ The points which satisfy this equation are all the points which are a distance of 3 from the origin. The graph is a circle centered on the origin with a radius of 3. We can see that this equation matches with option (C).