Which statements about $\mathrm{Zn}{}^{2+}$ are correct?

1. A$\mathrm{Zn}(\mathrm{OH}){}_2$ is a white precipitate that dissolves in excess $\mathrm{NaOH}$ as $[\mathrm{Zn}(\mathrm{OH}){}_4]{}^{2-}$.
2. B$\mathrm{K}{}_4[\mathrm{Fe}(\mathrm{CN}){}_6]$ gives a bluish-white (white) precipitate.
3. C$\mathrm{H}{}_2\mathrm{S}$ in ammoniacal medium gives white $\mathrm{ZnS}$ which dissolves in dilute $\mathrm{HCl}$.
4. DThe sulphide formed in ammoniacal medium is black.