Add the Proper Constant to Each Binomial So That the Resulting

Add the proper constant to each binomial so that the resulting trinomial is a perfect square trinomial. Then factor the
trinomial.
- $x ^ { 2 } + \frac { 1 } { 3 } x +$ ____

A) $x ^ { 2 } + \frac { 1 } { 3 } x + \frac { 1 } { 9 } = \left( x + \frac { 1 } { 3 } \right) ^ { 2 }$
B) $x ^ { 2 } + \frac { 1 } { 3 } x + \underline { 36 } = ( x + 6 ) ^ { 2 }$
C) $x ^ { 2 } + \frac { 1 } { 3 } x + \frac { 1 } { 6 } = \left( x + \frac { 1 } { 3 } \right) ^ { 2 }$
D) $x ^ { 2 } + \frac { 1 } { 3 } x + \frac { 1 } { \underline { 36 } } = \left( x + \frac { 1 } { 6 } \right) ^ { 2 }$