Photosynthesis differs from cellular respiration primarily because it involves light. Specifically, photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose, using carbon dioxide and water, and releasing oxygen as a byproduct. In contrast, cellular respiration is the process by which living organisms convert glucose and oxygen into energy (ATP), releasing carbon dioxide and water as byproducts.
So, the correct response is: The process involves light.