Searching a systematics for nonfactorizable contributions to hadronic decays of $D^0$ and $D^{+}$ mesons

We investigate nonfactorizable contributions to charm meson decays in $ D \rightarrow \bar K \pi $\mathrm{/}$ \bar K \rho$\mathrm{/}$ \bar K ^{} \pi$\mathrm{/}$ \bar K a_{1}$\mathrm{/}$ \bar K ^{} \rho $ modes. Obtaining the contributions from spectator-quark diagrams for $N_c$ = 3, we determine nonfactorizable isospin 1/2 and 3/2 amplitudes required to explain the data for these modes. We observe that ratio of these amplitudes seem to follow a universal value.