Answer:
D)photosynthesis
Step-by-step explanation
Photosynthesis is the major source of atmospheric oxygen on Earth. During photosynthesis, plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce glucose (a form of stored energy) and release oxygen as a byproduct. This process occurs in the chloroplasts of plant cells and in specialized organelles in algae and bacteria.(that's just a further explanation (; ) but somehow,the other options do not directly contribute the production of atmospheric oxygen.