Answer: The by-product of photosynthesis is oxygen.
Explanation: The photosynthesis process is the process by which photoautotrophs convert light energy into chemical energy which can later be used to fuel the activities of organisms. The three important elements required for the photosynthesis process are Water, carbon dioxide and light. The product formed from this process, stored in the form of sugars, which are created from water and carbon dioxide. The by-product of the photosynthesis process is oxygen.
6CO2 + 6H2O → C6H12O6 + 6O2