Which mixture of gasses is thought to have made up earths wary atmosphere

The mixture of gases that is thought to have made up Earth's early atmosphere is hydrogen, water vapor, ammonia, methane, carbon dioxide. This is previous to life so oxygen was not present because it was produced when green plants existed to produce oxygen through photosynthesis. Ozone was absen and so the UV radiation entered the atmosphere and it is thought that (along with electrical discharges) could vave contributed to the formation of the first organic molecules from the given mixture of inorganic gases.

a. decomposes use carbon from dead organisms as fuel for cellular respiration, returning carbon dioxide back into the atmosphere.

because the light is a great source of energy for the plants to survive. (i hope this )