Concept:The principal ore is the main natural mineral source from which a metal is extracted.
Explanation:Iron is commercially extracted from its principal ore in a blast furnace.
That principal ore is hematite, with the chemical formula
Fe2O3.
Hematite is abundant and has a high iron content, making it the most important iron ore.
Magnetite is also an iron ore, but it is not the principal one used for extraction.
Bauxite is the main ore of aluminium, not iron.
Calcite is a calcium carbonate mineral, unrelated to iron extraction.
Answer:D. Hematite.