The correct option is B vitrol chambers
The production of sulphuric acid by the assistance of the oxides of the nitrogen is carried out in the vitriol chambers. These are immense receptacles, mostly from 100 to 200 ft. long, 20 to 30 ft. wide, and 15 to 25 ft. high, constructed of sheet-lead, the joints of the sheets being made by burning or autogenous soldering.