Under Standard-State Conditions, Which of the Following Half-Reactions Occurs at the Cathode

Under standard-state conditions, which of the following half-reactions occurs at the cathode during the electrolysis of aqueous nickel sulfate at 25°C?

A) 2H₂O $\rarr$ O₂ + 4H⁺ + 4e^-
B) Ni²⁺ + 2e^- $\rarr$ Ni
C) 2H₂O + 2e^- $\rarr$ H₂ + 2OH^-
D) Ni $\rarr$ Ni²⁺ + 2e^-