Answer:
Option (C)
Explanation:
In the primitive world, about billions of years back, the initially formed organisms such as algae, were responsible for the production of large amount of oxygen in the atmosphere. This was possible by these algae, as they were able to carry out the process of photosynthesis, where the food is synthesized in the presence of sunlight, water and carbon dioxide (CO₂), and in return, it generates food and oxygen, on which the organisms are dependent on.
Thus, these algae were responsible for the changes in the atmosphere, by converting carbon dioxide (CO₂) into oxygen.
So, the correct answer is option (C).
