The atmosphere of early Earth probably contained no O2 until the emergence of organisms that . View Available Hint(s) The atmosphere of early Earth probably contained no O2 until the emergence of organisms that . used water as an electron source for photosynthesis used hydrogen sulfide as an energy source were chemoautotrophic had chloroplasts were oxygen respiring

Option (1)

Explanation:

The primitive atmosphere of the earth was comprised of little or no oxygen. After the appearance of the first primitive organisms in the oceans and other water bodies, they started to use the water as a source of electron that helped them to carry out the photosynthesis process. The primitive organisms such as cyanobacteria were able to carry out this process, in the presence of sunlight, CO₂ and water, and in return, it produced the oxygen, mostly in the form of dissolved oxygen.

Thus, the correct answer is option (1).