Add or Subtract as Indicated $\left( 3 x ^ { 7 } - 6 x ^ { 4 } \right) + \left( 6 x ^ { 7 } - 9 x ^ { 4 } - 2 \right)$

Multiple Choice

Add or subtract as indicated. Express the answer as a single polynomial in standard form.
- $\left( 3 x ^ { 7 } - 6 x ^ { 4 } \right) + \left( 6 x ^ { 7 } - 9 x ^ { 4 } - 2 \right)$

A) $3 x ^ { 7 } - 6 x ^ { 4 } - 2 x$
B) $9 x ^ { 7 } - 15 x ^ { 4 } - 2$
C) $- 2 x - 15 x ^ { 7 } - 5 x ^ { 4 }$
D) $- 11 \mathrm { x } ^ { 12 }$