Which of the following is classified as a secondary (rechargeable) cell?

Primary cells (dry, mercury, alkaline) undergo irreversible chemical changes during discharge and cannot be reliably recharged. The lead-acid (lead-storage) battery used in automobiles is a secondary cell because the discharge reaction at the electrodes can be reversed by passing current in the opposite direction, regenerating $\mathrm{Pb}$ and $\mathrm{PbO_2}$ from $\mathrm{PbSO_4}$.