In the cyanide process, native silver is leached with dilute aqueous $\mathrm{NaCN}$ in the presence of air. The soluble silver species formed is

1. A$\mathrm{AgCN}$
2. B$\mathrm{Na}{}_3[\mathrm{Ag}(\mathrm{CN}){}_4]$
3. C$\mathrm{Na}{}_2[\mathrm{Ag}(\mathrm{CN}){}_3]$
4. D$\mathrm{Na}[\mathrm{Ag}(\mathrm{CN}){}_2]$