Concept:Calcination is the strong heating of an ore in limited air to remove volatile impurities and moisture.Explanation:Carbonate ores decompose and release CO2​.Example: CuCO3​Δ​CuO+CO2​.Hydrated ores lose water of hydration as H2​O.Example: Fe2​O3​⋅3H2​OΔ​Fe2​O3​+3H2​O.So the gas given out depends on the type of ore.H2​S is not a usual product of calcination.Answer:Option C: either CO2​ or H2​O from hydrates is given out, depending on the type of ore.