In the set of four lead compounds Pb (II) compounds are PbO and PbSO4.PbO2 is a Pb (IV) compound whereas Pb3O4 is a mixed oxide of Pb (II) and Pb (IV) i.e. 2PbO⋅PbO2. Pb is a member of group 14 and it shows +2 and +4 oxidation states. But due to inert pair effect, Pb2+ is more stable than Pb4+.So,Pb (IV) compounds are strong oxidising agents as Pb4+ gets easily reduced to more stable Pb2+. Pb+4+2e−⟶Pb2+,∆C∘<0 (spontaneous) So, PbO2 or Pb3O4 can be the compound A. But out of these two compounds only PbO2 is used in lead storage batteries where a grid of lead packed with PbO2 acts as cathode and also it is amphoteric in nature. It reacts with both acids and alkali. (i) PbO2+2HCl⟶PbCl2+Cl2+H2O Here, PbO2 acts as a basic oxide as well as an oxidising agent. (ii) PbO2+2NaOH⟶Na2PbO2+H2O Here, PbO2 acts as an acidic oxide. So, the compound A is PbO2 (option-a).