Blister copper is refined by stirring molten impure metal with green logs of wood because such wood liberates hydrocarbon gases (like $CH_4$). This process $X$ is called . . . . . . . . . and the metal contains impurities of $Y$ is . . . . . . . . .

• A
  $X = \text{cupellation}, Y = CuO_2$
• B
  $X = \text{poling}, Y = Cu_2O$
• C
  $X = \text{poling}, Y = CuO$
• D
  $X = \text{cupellation}, Y = CuO$