The correct answer is C) pour the acid into the distilled water in a glass container. The reasoning is that when mixing electrolyte for a lead-acid storage battery, it is important to pour the more concentrated acid into the distilled water, rather than the other way around. This helps to control the exothermic reaction and prevent potentially dangerous spattering. Additionally, a glass container is recommended to avoid any potential chemical reactions with the container material. The other options are incorrect because pouring the water into the acid (A and B) can lead to uncontrolled reactions, and a zinc-plated container (B and D) may not be suitable due to potential interactions between the zinc and the battery electrolyte.