Which represents calcination?

• A. 2 Zn + O2 → 2 ZnO
• B. 2 ZnS + 3 O2 → 2 ZnO + 2 SO2
• C. MgCO3 → MgO + CO2
• D. 2 Ag + 2 HCl + [O] → 2 AgCl + H2O