Use the Laws of Exponents to Simplify Each Expression Using $x ^ { 9 } x ^ { - 6 }$

Multiple Choice

Use the laws of exponents to simplify each expression using positive exponents only. Assume all variables represent nonzero real numbers.
- $x ^ { 9 } x ^ { - 6 }$

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