Is the following expression a polynomial? Justify your answer:
$\frac{1}{5 x^{-2}}+5 x+7$

(A) Given expression: $\frac{1}{5 x^{-2}}+5 x+7$
Using the law of exponents $\frac{1}{x^{-n}} = x^n$,we can rewrite the expression as:
$\frac{1}{5} x^{2}+5 x+7$
In this expression,the exponents of the variable $x$ are $2$,$1$,and $0$ (since $7 = 7x^0$).
Since all exponents of the variable $x$ are non-negative integers (whole numbers),the given expression is a polynomial.