Simplify the Expression $\left(n^{9}\right)^{-2}$ A) $\frac{1}{n^{7}}$ B) $n^{7}$ C) $n^{18}$ D) $\frac{1}{n^{18}}$

Multiple Choice

Simplify the expression. Write the result without using negative exponents. (Assume all variables represent nonzero real numbers.)
- $\left(n^{9}\right) ^{-2}$

A) $\frac{1}{n^{7}}$
B) $n^{7}$
C) $n^{18}$
D) $\frac{1}{n^{18}}$