Simplify the Following Algebraic Expression and Express Your Answer Using $x ^ { 6 } x ^ { - 3 }$

Multiple Choice

Simplify the following algebraic expression and express your answer using positive exponents only. $x ^ { 6 } x ^ { - 3 }$

A) $x ^ { 9 }$
B) $\frac { 1 } { x ^ { 9 } }$
C) $x ^ { 3 }$
D) $\frac { 1 } { x ^ { 3 } }$