Factor the Polynomial Completely $9 x ^ { 2 } + 16$

Multiple Choice

Factor the polynomial completely. $9 x ^ { 2 } + 16$

A) $( 3 x + 1 ) ( 3 x - 16 )$
B) $\left( 3 x ^ { 2 } + 4 \right) ( 3 x - 4 )$
C) $( 9 x + 4 ) ( x - 4 )$
D) $( 3 x + 4 ) ( 3 x - 4 )$
E) not factorable