An impure copper anode contains Zn, Fe, Ag and Au. Standard reduction potentials (V): $\mathrm{Zn}{}^{2+}/\mathrm{Zn}$ $-0.76$, $\mathrm{Fe}{}^{2+}/\mathrm{Fe}$ $-0.44$, $\mathrm{Cu}{}^{2+}/\mathrm{Cu}$ $+0.34$, $\mathrm{Ag}{}^{+}/\mathrm{Ag}$ $+0.80$, $\mathrm{Au}{}^{3+}/\mathrm{Au}$ $+1.50$. In refining at a cell voltage only slightly above that needed for $\mathrm{Cu}$ dissolution and deposition in acidified $\mathrm{CuSO}{}_4$, which description is correct?

1. AZn and Fe dissolve and deposit on the cathode with Cu, while Ag and Au fall as mud
2. BAg and Au dissolve and remain in solution, while Zn and Fe form the anode mud
3. CZn and Fe dissolve and remain as ions in the electrolyte, Ag and Au fall as anode mud, and only Cu deposits at the cathode
4. DOnly Cu dissolves from the anode, so all other metals fall as mud