Four one litre flasks are separately filled with the gases H2,  He,  O2  and  O3  at the same temperature and pressure. The ratio of total number of atoms of these gases present in different flask would be

According to Avogadro's  law , at constant Temperature & pressure, equal volumes of gases contain equal number of molecules                                                                                                                                                           H2  :  He   :  O2   :   O3Ratio of total no. of molecules            =       1   :    1    :   1   :   1So ratio of total no. of atoms               =       2   :    1    :   2   :   3