Correct Answer: (a) Sulfuric acid
Solution:A lead-acid battery (or lead storage battery) is a rechargeable battery primarily used in automobiles. The electrolyte in these batteries is an aqueous solution of sulfuric acid (HβSOββ). During discharge, sulfuric acid reacts with the lead plates, and during charging, the process is reversed. The concentration of sulfuric acid changes during discharge and charge cycles, which is why a hydrometer can be used to check the battery's state of charge.