Find the Term That Should Be Added to the Expression $x^{2}+12 x$

Multiple Choice

Find the term that should be added to the expression to form a perfect square trinomial. Write the resulting perfect square trinomial in factored form.
- $x^{2}+12 x$

A) $36 ;(x+6) ^{2}$
B) 0 ; $(x+6) ^{2}$
C) $144 ;(x+12) ^{2}$
D) $36 ;(x-6) ^{2}$