Which gas was absent in the atmosphere at the time of origin of life?

Gases that were present at the time of origin of life are ammonia, hydrogen, nitrogen, carbon dioxide, methane, and water vapour. Oxygen was formed at a very later stage. Therefore, the gas which was absent at the time of origin of the earth is oxygen.

Since, all gases except oxygen given in options are present at the time of origin of earth, correct option is (c) oxygen.