Which one of the following oxoacids of phosphorus can reduce $AgNO_3$ to metallic silver?

$Assertion :$ Nitrogen and oxygen are the main components in the atmosphere but these do not react to form oxides of nitrogen.
$Reason :$ The reaction between nitrogen and oxygen requires high temperature.

Which of the following has the lowest boiling point?

How many numbers of $P-OH$ and $P-O-P$ bonds are present in pyrophosphoric acid respectively?

Lapis lazuli is

White phosphorus reacts with thionyl chloride to give