<prompt> Maximum contribution to atomospheric air is-N2O2CO2Helium  <response>: Ans. is a i.e., N2 The constituents of air:- Major - Nitrogen N2 - 78.1 , Oxygen O2 - 20.93, Carbon dioxide CO2 - 0.03 Minor - Argon, neon, krypton, xenon, helium, water vapour, traces fo ammonia, suspended matter dust, bacteria, spores, vegetable debris. 