Greetings!
First and foremost, let's define abiotic & biotic factors.
Abiotic factors are materials in an ecosystem that are non-living.
ex) rocks, wind, water, sunlight, etc.
Biotic factors are living organisms, anything with cells that can interact with it's environment.
So the correct answer would be A. Oxygen circulating throughout the atmosphere.
Hope this helps, have a nice day!
