The extraction of zinc from zinc blende is achieved by

What is the role of the graphite rod in the electrometallurgy of aluminium?

Cryolite $(Na_3AlF_6)$ helps in:

In the extraction of copper from its sulphide ore,the metal is finally obtained by the reduction of cuprous oxide with

In the electrolytic extraction of $Al$,molten cryolite $(Na_3AlF_6)$ is used because it .......

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: In the Ellingham diagram,a sharp change in slope of the line is observed for $Mg \rightarrow MgO$ at $\sim 1120^{\circ} C$.
Reason $R$: There is a large change of entropy associated with the change of state.
In the light of the above statements,choose the correct answer from the options given below.