The Final Step of the Purification of Copper Involves Electrorefining

Multiple Choice

The final step of the purification of copper involves electrorefining in which copper is separated from nickel and iron by being reduced at the cathode of a cell. Why are nickel and iron not reduced?

A) Their reduction potentials are more positive than copper's.
B) Their reduction potentials are more negative than copper's.
C) They cannot be deposited on a copper electrode.
D) Their reduction potentials are more negative than water's.
E) Their reduction requires large overvoltages.