Question

The main ore used in the extraction of iron is:(a) Haematite(b) Calamine(c) Bauxite(d) Cryolite

Hint: The name of the iron ore is derived from the Greek word haima which means blood since it has red colouration in some of its varieties. Due to its red colour, it is also used as a pigment.

Let us look at the ores one by one.
Calamine is the ore of Zinc. It consists of two distinct minerals namely smithsonite (zinc carbonate) and hemimorphite (zinc silicate).
Bauxite is the ore of aluminium and gallium. It consists of minerals such as gibbsite (aluminium hydroxide), boehmite ($\gamma -AlO(OH)$) and diaspore ($\alpha -AlO(OH)$) along with haematite (Ferric oxide), kaolinite (${ Al }_{ 2 }{ Si }_{ 2 }{ O }_{ 5 }(OH)$), anatase (Titanium dioxide), ilmenite ($FeO.{ TiO }_{ 2 }$) and goethite ($FeO(OH)$).
Cryolite (sodium hexafluoroaluminate) is a mineral which is used as a solvent for refining aluminium in the Hall-Heroult process, as an insecticide, pesticide and as a colouring agent in fireworks.
Haematite is the ore of Iron. It is an oxide of iron (ferric oxide) and is found in rocks and soil. For the extraction of iron from the ore, haematite along with carbon (coke) and limestone are added to the blast furnace. Ferric oxide in the Haematite ore is reduced using carbon and carbon monoxide at different sections of the blast furnace that are at different temperatures. The reactions are given below:
$Zone\quad of\quad combustion:C(s)+{ O }_{ 2 }(g)\xrightarrow { 2170\quad K } { CO }_{ 2 }(g)$
$Zone\quad of\quad heat\quad absorption:{ CO }_{ 2 }(g)+C(s)\xrightarrow { 1423\quad K } 2CO(g)$
$Zone\quad of\quad slag\quad formation:\begin{matrix} CaC{ O }_{ 3 }(s)\xrightarrow { 1123\quad K } CaO(s)+{ CO }_{ 2 }(g) \\ CaO(s)+Si{ O }_{ 2 }(s)\xrightarrow { 1123\quad K } CaSi{ O }_{ 3 }(s) \end{matrix}$
Zone of reduction:
$\begin{matrix} 3{ Fe }_{ 2 }{ O }_{ 3 }(s)+CO(g)\xrightarrow { 573-673\quad K } 2{ Fe }_{ 3 }{ O }_{ 4 }(s)+{ CO }_{ 2 }(g) \\ { Fe }_{ 3 }{ O }_{ 3 }(s)+4CO(g)\xrightarrow { 773-873\quad K } 3Fe(s)+4CO_{ 2 }(g) \\ { Fe }_{ 2 }{ O }_{ 3 }(g)+CO(g)\xrightarrow { 773-873\quad K } 2FeO(s)+{ CO }_{ 2 }(g) \\ FeO(s)+C(s)\xrightarrow { >1073\quad K } Fe(s/l)+CO(g) \\ { Fe }_{ 2 }{ O }_{ 3 }(s)+3C(s)\xrightarrow { >1073\quad K } 2Fe(s/l)+3CO(g) \end{matrix}$

Hence the correct answer is (a) Haematite.

Note:
Limestone is added in the blast furnace for the extraction of iron since limestone decomposes on heating and produces calcium oxide which acts as a flux. The calcium oxide combines with the silica which is present in the Haematite ore as impurity and forms calcium silicate slag.