A.
easy, remember rules of exponents
the only one you need to know for this question is this one: \frac{x^m}{x^n}=x^{m-n}
also x^{-m}=\frac{1}{x^m}
so in this case
\frac{5^5}{5^8}=5^{5-8}=5^{-3}=\frac{1}{5^3}
answer is 1st option
B.
same as A

answer is 1st option