Consider the Galvanic cell $Zn|ZnSO_4||CuSO_4|Cu$. The reaction at the cathode is

• A
  $Zn^{2+} + 2e^- \to Zn$
• B
  $Cu^{2+} + 2e^- \to Cu$
• C
  $Cu^{2+} + Zn \to Cu + Zn^{2+}$
• D
  $Zn^{2+} + Cu \to Zn + Cu^{2+}$