Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Aluminium is extracted from bauxite by the electrolysis of molten mixture of Al$$_2$$O$$_3$$ with cryolite.
Reason (R) : The oxidation state of Al in cryolite is +3.
In the light of the above statements, choose the most appropriate answer from the options given below:

Assertion (A): Aluminium is obtained industrially by the electrolysis of a molten mixture containing $$\text{Al}_2\text{O}_3$$ (alumina) dissolved in cryolite ($$\text{Na}_3\text{AlF}_6$$). This statement is TRUE because alumina alone has a very high melting point (about $$2050^\circ\text{C}$$). Adding cryolite lowers the melting point to nearly $$950^\circ\text{C}$$ and increases the electrical conductivity, making large-scale electrolysis feasible. Hence, (A) is correct.

Reason (R): In cryolite, $$\text{Na}_3\text{AlF}_6$$, let the oxidation state of Al be $$x$$.
Total charge on six fluoride ions $$=6(-1)=-6$$.
Total charge contributed by three sodium ions $$=3(+1)=+3$$.
The compound is electrically neutral, so
$$x + (+3) + (-6) = 0 \Longrightarrow x -3 = 0 \Longrightarrow x = +3$$.
Therefore the oxidation state of aluminium in cryolite is indeed $$+3$$. Hence, (R) is also correct.

Link between (A) and (R): The reason for introducing cryolite during electrolysis is to lower the melting point and improve conductivity, not because aluminium happens to be in the $$+3$$ oxidation state (Al is already in the $$+3$$ state in alumina as well). Thus, while (R) is a true statement, it does not explain why cryolite is mixed with alumina.

Therefore, both (A) and (R) are correct, but (R) is not the correct explanation of (A).

Option C is the most appropriate choice.