Question

At the time when earth originated there was large amount of methane and other hydrocarbons but now in the present atmosphere, it has been replaced by

• A. H${}_2$
• B. CO${}_2$
• C. O${}_2$
• D. N${}_2$

Answer 1

The correct option is C O${}_2$

During the origin of the earth, it had a reducing atmosphere in which gases like hydrogen, helium, nitrogen, carbon dioxide, ammonia, methane, etc. along with some amount of water vapor were present. Later, with the origin of life, the geochemical and biochemical cycles that came into play had a great influence over the atmosphere of the earth. The process of photosynthesis resulted in the decrease of carbon dioxide in the atmosphere whereas the bio-molecules were formed from other hydrocarbons. Thus, the reducing atmosphere gradually changed into an oxidizing atmosphere with increasing amount of oxygen with other gases present in it.

So, the correct answer is ' O${}_2$ '.