Radius ratio $r_{+}/r_{-}$ is computed from these radii (pm): $\mathrm{Zn}{}^{2+}$ 74, $\mathrm{S}{}^{2-}$ 184; $\mathrm{Cs}{}^{+}$ 169, $\mathrm{Cl}{}^{-}$ 181; $\mathrm{Mg}{}^{2+}$ 72, $\mathrm{O}{}^{2-}$ 140; $\mathrm{Be}{}^{2+}$ 35, $\mathrm{O}{}^{2-}$ 140. Using the ranges 0.225-0.414 (tetrahedral, CN 4), 0.414-0.732 (octahedral, CN 6) and 0.732-1 (cubic, CN 8), which predictions are correct?

1. A$\mathrm{ZnS}$ (ratio 0.402) is tetrahedral with CN 4.
2. B$\mathrm{BeO}$ (ratio 0.250) is tetrahedral with CN 4.
3. C$\mathrm{MgO}$ (ratio 0.514) is tetrahedral with CN 4.
4. D$\mathrm{CsCl}$ (ratio 0.934) has CN 8.