Carbon and $CO$ gas are used to reduce which of the following pairs of metal oxides for the extraction of metals?

Among the following,the main reactions occurring in the blast furnace during the extraction of iron from haematite are:
$i$. $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
$ii$. $FeO + SiO_2 \rightarrow FeSiO_3$
$iii$. $Fe_2O_3 + 3C \rightarrow 2Fe + 3CO$
$iv$. $CaO + SiO_2 \rightarrow CaSiO_3$

Out of $C$ and $CO$,which is a better reducing agent for $ZnO$?

Assertion : Coke and flux are used in smelting.
Reason : The phenomenon in which ore is mixed with suitable flux and coke is heated to fusion is known as smelting.

Explain the leaching and oxidation-reduction process in the metallurgy of gold.

Write down the reactions taking place in the blast furnace related to the metallurgy of iron in the temperature range $500-800 \ K$.