Which of the following is the anhydride of nitrous acid?

Reaction of thionyl chloride with white phosphorus forms a compound $[A]$,which on hydrolysis gives $[B]$,a dibasic acid. $[A]$ and $[B]$ are respectively

$A$ metal $(X)$ dissolves in both dilute $HCl$ and dilute $NaOH$ to liberate $H_2$ gas. Addition of $NH_4Cl$ and excess $NH_4OH$ to an $HCl$ solution of $(X)$ produces $(Y)$ as a precipitate. $(Y)$ is also produced by adding $NH_4Cl$ to the $NaOH$ solution of $(X)$. The species $(X)$ and $(Y)$,respectively,are:

Chemical nature of the nitrogen oxide compound obtained from a reaction of concentrated nitric acid and $P_{4}O_{10}$ (in $4:1$ ratio) is:

Which oxide is alkaline?

Which of the following oxides does not give any oxyacid in aqueous solution?