An ore of metal $'M'$ $\xrightarrow{\text{Roasting}}$ Metal oxide $\xrightarrow{\text{carbon reduction}}$ $'M'$
(After crushing and grinding)
$'M'$ may be :-

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.

In the extraction of which of the following,a complex ion is formed?

In the electrolysis of aluminium oxide,which of the following is added to accelerate the process?

In the commercial electrochemical process for aluminium extraction,the electrolyte used is:

Aluminium is produced on a large scale by electrolysis of alumina,dissolved in fused cryolite and a little fluorspar. These two electrolytes,cryolite and fluorspar are respectively