Factor by Any Method $$4 x ^ { 2 } + a x + 16$$

Multiple Choice

Factor by any method.
-Find all values of a that will make the polynomial a perfect square trinomial. $$4 x ^ { 2 } + a x + 16$$

A) $16 , - 16$
B) 16
C) 8
D) $8 , - 8$