Question

Which of the following gases was not believed to be present on earth at the time of its formation 4.6 billion years ago?

Answer 1

Almost possitive it is oxygen cause there was no ozone

Answer 2

The correct answer is Oxygen

When the early earth was formed there were no oxygen in the atmosphere of earth although it was present in the interiors of the earth. The atmosphere of earth was not always full of oxygen as of now, the cyanobacteria were the first organisms to produce oxygen on earth's atmosphere by the process of photosynthesis. After the evolution of oxygen on earth the animals like dinosaur and other reptiles evolved on earth.