Borax dissolves in water and forms a product of boron $(X)$. Identify the compound $X$.

$A$ 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. $H_{2}SO_{4}$ is added to a hot solution of $X,$ white crystals of an acid $Z$ separate out.
Write equations for all the above reactions and identify $X, Y,$ and $Z$.

The correct orders among the following are
$A$. Atomic radius $: B < Al < Ga < In < Tl$
$B$. Electronegativity $: Al < Ga < In < Tl < B$
$C$. Density $: Tl < In < Ga < Al < B$
$D$. $1^{st}$ Ionisation Energy $: In < Al < Ga < Tl < B$
Choose the correct answer from the options given below $:$

Boron halides behave as Lewis acids because of their nature.

Hydrated $AlCl_3$ is used as :

The type of hybridisation of boron in diborane is