Factor the Following Perfect Square Trinomial $$a ^ { 2 } + 6 a + 9$$

Multiple Choice

Factor the following perfect square trinomial. $$a ^ { 2 } + 6 a + 9$$

A) $( a - 3 ) ^ { 2 }$
B) $( a + 2 ) ^ { 2 }$
C) $( a + 6 ) ^ { 2 }$
D) $( a + 3 ) ^ { 2 }$
E) none of these