Simplify Assume That Variables in the Exponent Represent Nonzero Integers $\frac { \left( x ^ { a } + 3 \right) ^ { 6 } } { \left( x ^ { a - 4 } \right) ^ { 3 } }$

Multiple Choice

Simplify. Assume that variables in the exponent represent nonzero integers and that all other variables are not 0.
- $\frac { \left( x ^ { a } + 3 \right) ^ { 6 } } { \left( x ^ { a - 4 } \right) ^ { 3 } }$

A) $3 x ^ { 7 }$
B) $x ^ { 9 a + 30 }$
C) $x ^ { 3 a + 30 }$
D) $x ^ { a } + 30$