Diffusion is important to organisms because it is the process by which useful molecules enter the body cellsand waste products are removed. Digested food molecules (amino acids, glucose) move down a concentration gradient from the intestine to the blood.
I think the answer you are looking for is oxidative phosphorylation! :)
Archaea actually are a domain! Originally they were thought to be bacteria, but have since been classified in their own domain: archaea.
The right answer is D) photosynthesis in plants
Cellular respiration does not produce oxygen, it consumes it rather. The same for the respiration of animals and the human being.
The degradation of organic matter does not produce oxygen.
Photosynthesis is the only one of these proposals that produces oxygen, and this process belongs to the plants.