  The dynamical fluctuations of kaon--to--pion ratios have been studied over a
wide range of center--of--mass energies $\sqrt{s}$. Based on changing phase
space volume which apparently is the consequence of phase transition from
hadrons to quark--gluon plasma at large $\sqrt{s}$, single--particle
distribution function $f$ is assumed to be rather modified. Varying $f$ and
phase space volume are implemented in the grand--canonical partition function,
especially at large $\sqrt{s}$, so that hadron resonance gas model, when taking
into account the experimental acceptance and quark phase space occupation
factor, turns to be able to reproduce the dynamical fluctuations over the
entire range of $\sqrt{s}$.
