The correct answer is A) pour the acid into the distilled water. When mixing the electrolyte for a lead-acid battery, the proper procedure is to slowly pour the concentrated sulfuric acid into the distilled water. This is to avoid a dangerous exothermic reaction that can occur if the water is poured into the acid. Pouring the acid into the water allows the heat to dissipate safely and prevents the solution from splashing. The other options, B, C, and D, are incorrect as they involve pouring the water into the acid, which is an unsafe method that can lead to an uncontrolled reaction.