Which of the following reactions occurs at the cathode during the recharging of a lead storage battery?

• A
  $PbSO_4(s) + 2H_2O(\ell) \rightarrow PbO_2(s) + SO_4^{2-}(aq.) + 4H^+(aq.) + 2e^-$
• B
  $PbO_2(s) + 4H^+(aq.) + SO_4^{2-}(aq.) + 2e^- \rightarrow PbSO_4(s) + 2H_2O(\ell)$
• C
  $Pb(s) + SO_4^{2-}(aq.) \rightarrow PbSO_4(s) + 2e^-$
• D
  $PbSO_4(s) + 2e^- \rightarrow Pb(s) + SO_4^{2-}(aq.)$