Compound A used as a strong oxidizing agent is amphoteric in nature. It is the part of lead storage batteries. Compound A is:

We need to identify compound A which is: (i) a strong oxidizing agent, (ii) amphoteric in nature, and (iii) used in lead storage batteries.

In a lead storage battery, the cathode (positive plate) is made of $$PbO_2$$ (lead dioxide) and the anode (negative plate) is made of Pb. During discharge, $$PbO_2$$ acts as a strong oxidizing agent, getting reduced to $$PbSO_4$$.

$$PbO_2$$ is amphoteric — it can react with both acids and bases. With acids: $$PbO_2 + 4HCl \to PbCl_2 + Cl_2 + 2H_2O$$. With bases: $$PbO_2 + 2NaOH \to Na_2PbO_3 + H_2O$$ (forming plumbate).

Checking the other options: PbO is amphoteric but not a strong oxidizing agent used in lead storage batteries. $$Pb_3O_4$$ (red lead) is not a primary component of lead storage batteries. $$PbSO_4$$ is the discharge product, not an oxidizing agent.

Therefore, compound A is $$\mathbf{PbO_2}$$.