A non-metal A which is the largest constituent of air, when heated with H2 in 1 : 3 ratio in the presence of catalyst (Fe) gives a gas B. 0n heating with `O_(2)` it gives an oxide C. If this oxide is passed into water in the presence of air, it gives an acid D which acts as a strong oxidising agent. 
(a) Identify A, B, C and D.
(b) To which group of the periodic table does this non-metal belongs? 

Explanation

A is nitrogen (the largest component of air - 78%), B is ammonic, C is nitrogen dioxide and D is nitric acid (a strong oxidizing agent).