Concept:Preferential discharge of ions depends on which ion is released more easily at an electrode during electrolysis.
Explanation:At each electrode, different ions compete for discharge.
The key influencing factors are the position of the ions in the electrochemical series, the concentration of the ions in the electrolyte, and the nature of the electrode.
Among the options given, only the nature of the electrode directly affects this preferential discharge.
The mechanism, electrolytic reactions, and type of cell do not directly determine which ion is discharged first.
Answer:C. nature of the electrode