Select the correct statements about copper(II) in the qualitative scheme.

1. AExcess $\mathrm{KCN}$ reduces $\mathrm{Cu}{}^{2+}$ to copper(I), which is held as a cyano complex (cyanogen is evolved).
2. B$\mathrm{CuS}$ dissolves in yellow ammonium sulphide, so copper is placed in group IIB.
3. CA little $\mathrm{NH}{}_3$ gives a pale blue basic precipitate, which dissolves in excess $\mathrm{NH}{}_3$ to give deep blue $[\mathrm{Cu}(\mathrm{NH}{}_3){}_4]{}^{2+}$.
4. D$\mathrm{K}{}_4[\mathrm{Fe}(\mathrm{CN}){}_6]$ gives chocolate-brown $\mathrm{Cu}{}_2[\mathrm{Fe}(\mathrm{CN}){}_6]$.