The Production of Nickel and Copper Metals from Their Ores

The production of nickel and copper metals from their ores involves sulfur dioxide emissions because

A) the ores of these elements are composed primarily of NiSO₂ and CuSO₂.
B) the ores of these elements are composed primarily of NiS and CuS.
C) to release the metals from their ores,the ores are heated with sulfur-containing coal.
D) the release of metals from their ores involves the reaction of SO₃ with the ore.