Factor the GCF Out of the Given Expression $$9 a ^ { 6 } + 36 a ^ { 4 }$$

Multiple Choice

Factor the GCF out of the given expression.
- $$9 a ^ { 6 } + 36 a ^ { 4 }$$

A) $a ^ { 4 } \left( 9 a ^ { 2 } + 36 \right)$
B) $9 a ^ { 4 } \left( a ^ { 2 } + 4 \right)$
C) $36 \left( a ^ { 2 } + 4 a \right)$
D) $9 \left( a ^ { 6 } + 4 a ^ { 4 } \right)$