Below are two statements, one labeled as Assertion $(A)$ and the other as Reason $(R):$

Assertion $(A)$: Among group $13$ elements, boron's melting point is unusually high $(2453 \mathrm{~K})$.

Reason $(R):$ Solid boron has a strong crystalline lattice.

In the context of the above statements, choose the correct answer from the following options:

Alumina is insoluble in water because

A certain salt $X$, gives the following results.

$(i)$ Its aqueous solution is alkaline to litmus.

$(ii)$ It swells up to a glassy material $Y$ on strong heating.

$(iii)$ When conc. $H_2SO_4$ is added to a hot solution of $X$, white crystal of an acid $Z$ separates out.

Write equations for all the above reactions and identify $X, Y$ and $ Z$.

Give chemical reaction of aluminum with dilute $HCl$ ? 

The purification of alumina is called