Which Answer Is a Polar Form of the Given Rectangular $$x ^ { 2 } + y ^ { 2 } = 25$$

Multiple Choice

Which answer is a polar form of the given rectangular equation?
$$x ^ { 2 } + y ^ { 2 } = 25$$

A) $r = 5$
B) $r = 25$
C) $r ^ { 2 } + \theta ^ { 2 } = 25$
D) $\theta = 25$
E) $\theta = 5$