Why is $N_2$ chemically inert?

Phosphorus can be stored in

Which of the following represents the correct order of the inert pair effect in Group $13$ elements?

Which of the following oxides of nitrogen is the anhydride of nitrous acid?

$A$ tetra-atomic molecule $(A)$ on reaction with nitrogen $(I)$ oxide,produces two substances $(B)$ and $(C).$ $(B)$ is a dehydrating agent in its monomeric form while substance $(C)$ is a diatomic gas which shows almost inert behaviour. The substances $(A)$,$(B)$,and $(C)$ respectively will be

Which one of the following elements occurs free in nature?