Which of the following chemical equations represents the hydrometallurgical process for the extraction of copper from its ore?

• A
  $Cu^{2+} (aq) + H_2 (g) \rightarrow Cu (s) + 2H^+ (aq)$
• B
  $Cu^{2+} (aq) + Fe (s) \rightarrow Cu (s) + Fe^{2+} (aq)$
• C
  $Cu_2S + 2Cu_2O \rightarrow 6Cu + SO_2$
• D
  $Cu_2S + H_2 \rightarrow 2Cu + H_2S$