Final answer:
Photosynthesis is the fastest process at releasing oxygen into the atmosphere. It far surpasses other processes like decay, weathering, and aerobic respiration, which consume oxygen rather than produce it.
Step-by-step explanation:
The fastest process at releasing oxygen into the atmosphere is photosynthesis. This biological process, performed by plants and other photosynthetic organisms, uses sunlight to convert carbon dioxide and water into glucose and free oxygen. Photosynthesis is crucial for life on Earth as it produces the oxygen used by most organisms for aerobic respiration and supports the food chains.
Oxygen is also produced in lesser amounts through photodissociation in the upper atmosphere, but this source is not as significant as photosynthesis. Other processes like decay, weathering, and aerobic respiration do not release oxygen; in fact, they consume it. Therefore, photosynthesis as the correct answer to our question is by far the most significant source of atmospheric oxygen.