Which Answer Is a Rectangular Form of the Given Polar $r = 18 \cos \theta$

Multiple Choice

Which answer is a rectangular form of the given polar equation?
$r = 18 \cos \theta$

A) $( x - 9 ) ^ { 2 } + y ^ { 2 } = 81$
B) $( x + 9 ) ^ { 2 } + y ^ { 2 } = 81$
C) $( x + 9 ) ^ { 2 } + y ^ { 2 } = 9$
D) $x ^ { 2 } + ( y + 9 ) ^ { 2 } = 81$
E) $x ^ { 2 } + ( y - 9 ) ^ { 2 } = 81$