The correct answer is C. Smelting.
Dressing is the process of removing impurities from the ore. Calcination is the process of heating the ore to a high temperature to remove water and other volatile compounds. Roasting is the process of heating the ore to a high temperature in the presence of air to convert it into a more easily fusible form.
Smelting is the process of extracting metal from its ore by heating it to a high temperature and then reducing it with a reducing agent, such as carbon. In the case of iron, the ore is heated to a high temperature in a blast furnace, where it is reduced by carbon monoxide gas. The molten iron is then poured into molds to form pig iron.
Pig iron is a cast iron that is high in carbon content. It is used in the production of steel and other iron-based alloys.