Simplify the Expression $$\left( 13 a ^ { 2 } + 6 a + 9 \right) + \left( 8 a ^ { 2 } + 9 a + 1 \right)$$

Multiple Choice

Simplify the expression. $$\left( 13 a ^ { 2 } + 6 a + 9 \right) + \left( 8 a ^ { 2 } + 9 a + 1 \right)$$

A) $21 a ^ { 2 } + 6 a + 10$
B) $21 a ^ { 2 } + 15 a + 10$
C) $21 a ^ { 2 } + 15 a$
D) $13 a ^ { 2 } + 15 a + 10$
E) none of these