Simplify Assume That All Exponents Represent Natural Numbers $\left( 8 x ^ { 2 r } - x ^ { r } - 1 \right) + \left( x ^ { 2 r } + 5 x ^ { r } + 3 \right)$

Multiple Choice

Simplify. Assume that all exponents represent natural numbers.
- $\left( 8 x ^ { 2 r } - x ^ { r } - 1 \right) + \left( x ^ { 2 r } + 5 x ^ { r } + 3 \right)$

A) $9 x ^ { 4 r } + 6 x ^ { 2 r } + 4$
B) $7 x ^ { 4 r } - 6 x ^ { 2 r } - 4$
C) $9 x ^ { 2 r } + 4 x ^ { r } + 2$
D) $8 x ^ { 2 r } + 5 x ^ { r } + 3$