The correct answer is (D) A large, heavy glass vessel, typically of 5 to 20 gallons in volume, that is used to contain and transport distilled water or acids or other corrosive liquids.

Examples of use:

• A full carboy of distilled water rested on the floor beside the water cooler.
  
  
• It required considerable strength to lift the carboy to his shoulder and carry it from the truck to the office at the top of the stairway.