The $pH$ of a 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?

• A
  Soap and detergent factory
• B
  Lead battery manufacturing factory
• C
  Plastic cup manufacturing factory
• D
  Alcohol distillery