The compound($s$) which react($s$) with $NH _3$ to give boron nitride ($BN$) is(are)

$(A)$ $B$ $(B)$ $B _2 H _6$ $(C)$ $B _2 O _3$ $(D)$ $HBF _4$

Anhydrous $AlCl_3$ is formed in

Conc. $HN{O_3}$

A layer of coke is spread over bauxite during electrolytic reduction of alumina by Hall-Heroult process. This layer acts as a/an:

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$:

Assertion $A$ : The stability order of +$1$ oxidation state of $\mathrm{Ga}$, In and $\mathrm{Tl}$ is $\mathrm{Ga}<\mathrm{In}<\mathrm{Tl}$.

Reason $R$ : The inert pair effect stabilizes the lower oxidation state down the group.

In the light of the above statements, choose the correct answer from the options given below :

The stability of $+ 1$ oxidation state among $Al,Ga, In$ and $Tl$ increases in the sequence