\textbf{126--} In a random experiment, $S=\{x,y,z\}$ is a sample space. If $P(x)$, $P(y)$, and $P(z)$ form a geometric sequence and together they are less than one unit and their geometric mean is $\dfrac{1}{5}$, then the smallest simple event in $S$ is how much?
\medskip
(1) $\dfrac{2-\sqrt{2}}{5}$ \hfill (2) $\dfrac{2-\sqrt{2}}{5}$ \hfill (3) $\dfrac{2-\sqrt{3}}{10}$ \hfill (4) $\dfrac{2-\sqrt{3}}{10}$
\bigskip