Which of the following is a cyclic phosphate?

On passing a gas,$X$,through Nessler's reagent,a brown precipitate is obtained. The gas $X$ is

$H_4P_4O_{12}$ and $H_3P_3O_9$ have the same:

$A + H_2O \to B + HCl$ and $B + 3H_2O \to C + 3HCl$. Compounds $(A)$,$(B)$,and $(C)$ are respectively:

$A$ 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:

Thallium shows different oxidation states because