Perform the Indicated Operations and Simplify $\left( 6 x ^ { 6 } + 5 x ^ { 3 } \right) + \left( 9 x ^ { 6 } + 6 x ^ { 3 } + 4 \right)$

Multiple Choice

Perform the indicated operations and simplify.
- $\left( 6 x ^ { 6 } + 5 x ^ { 3 } \right) + \left( 9 x ^ { 6 } + 6 x ^ { 3 } + 4 \right)$

A) $39 x ^ {10 }$
B) $18 x ^ { 6 } + 12 x ^ { 3 } + 4 x$
C) $4 x + 11 x ^ { 6 } + 13 x ^ { 3 }$
D) $15 x ^ { 6 } + 11 x ^ { 3 } + 4$