Laughing gas is prepared by heating

One of the acids listed below is formed from $P_2O_3$ and the rest are formed from $P_2O_5$. The acid formed from phosphorus $(III)$ oxide is

Phosphorus is manufactured by heating in an electric furnace a mixture of

What is the number of oxygen atoms attached to each phosphorus atom in $P_4O_{10}$?

The strongest reducing agent among the following is:

Phosphorus forms a number of oxoacids. Out of these oxoacids,phosphinic acid $(H_3PO_2)$ has strong reducing properties. Write its structure and also write a reaction showing its reducing behavior.