Iron is extracted from magnetite by reduction with

Limestone is used as a flux in the extraction of

Which is the main reducing agent for extraction in a blast furnace?

Which of the following metals is extracted by the electrolytic reduction method?

Given are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Magnesium can reduce $Al_{2}O_{3}$ at a temperature below $1350^{\circ} C$,while above $1350^{\circ} C$ aluminium can reduce $MgO$.
Reason $R$: The melting and boiling points of magnesium are lower than those of aluminium.
In light of the above statements,choose the most appropriate answer from the options given below:

In the extraction of silver by the Mac-Arthur-Forrest cyanide process,a small amount of $KNO_3$ is also added as a flux. The function of $KNO_3$ is