Four 1 litre flasks are separately filled with the gases hydrogen, helium, oxygen and ozone at the same temperature and pressure, the ratio of total number of atoms of these gases present in the different flasks would be

A. 3:2:2:1

B. 2:1:2:3

C. 1:2:2:3

D. 1:1:1:1

Please do not use chat terms. Example: avoid using "grt" instead of "great".