When the lead storage battery is in use (during discharge),the reaction that occurs at the anode is:

• A
  $PbSO_{4\text{(s)}} + 2H_2O_{\text{(l)}} \rightarrow PbO_{2\text{(s)}} + SO_4^{2-}{_{\text{(aq)}}} + 4H^{+}{_{\text{(aq)}}} + 2e^{-}$
• B
  $Pb_{(s)} + PbO_{2(s)} + 2H_2SO_{4(aq)} \longrightarrow 2PbSO_{4(s)} + 2H_2O(\ell)$
• C
  $Pb_{\text{(s)}} + SO_4^{2-}{_{\text{(aq)}}} \rightarrow PbSO_{4\text{(s)}} + 2e^{-}$
• D
  $PbO_{2\text{(s)}} + SO_4^{2-}{_{\text{(aq)}}} + 4H^{+}{_{\text{(aq)}}} + 2e^{-} \rightarrow PbSO_{4\text{(s)}} + 2H_2O_{\text{(l)}}$