When bauxite powder is mixed with coke and heated with nitrogen at $2075 \ K$,carbon monoxide and $x$ are formed. Which gas is produced when $x$ reacts with water?

Dinitrogen and dioxygen,the main constituents of air,do not react with each other in the atmosphere to form oxides of nitrogen because:

Nitrogen dioxide cannot be prepared by heating:

$A$ pungent smelling gas $A$ gives dense white fumes with conc. $HCl$. When $A$ reacts with an alkaline solution of a colourless reagent $B$,a reddish-brown precipitate $C$ is formed. The compounds $A, B, C$ respectively are:

Of the following compounds, the most acidic is:

Which gas is formed in the atmosphere due to lightning?