Perform the Operations and Simplify $$\left( 5 x ^ { 3 } - 6 x ^ { 2 } \right) + \left( 9 x ^ { 3 } - 3 x \right)$$

Multiple Choice

Perform the operations and simplify. $$\left( 5 x ^ { 3 } - 6 x ^ { 2 } \right) + \left( 9 x ^ { 3 } - 3 x \right)$$

A) $\quad 14 x - 6 x ^ { 2 } - 3 x ^ { 3 }$
B) $\quad 5 x ^ { 3 }$
C) 0
D) $\quad 14 x ^ { 3 } - 6 x ^ { 2 } - 3 x$