The pH of water sample collected from a river was found to be acidic in the range of 3.5 — 4.5, on the banks of the river were several factories that were discharging effluents into the river. The effluents of which one of the following factories is the most likely cause for lowering the pH of river water?

Lead battery manufacturing factory use acids in lead batteries which has lower pH and when discharged into nearby water bodies are more likely to lower pH value of water.