The common ratio \(r\) in a geometric progression is found by dividing any term by the previous term.
For the given G.P. \(25, -5, 1, -\frac{1}{5}, \dots\), the common ratio is:
\[
r = \frac{-5}{25} = -\frac{1}{5}
\]
Thus, the correct answer is option (1).