Option 1: Ammonia is not a product of the process of photosynthesis. Photosynthesis is the process where plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. Ammonia is a compound that is typically produced through the process of nitrogen fixation.

Option 2: Chlorine is not a product of photosynthesis. It is a chemical element that does not play a direct role in the process of converting sunlight into energy.

Option 3: Oxygen is the correct answer. During photosynthesis, plants produce oxygen as a byproduct. This oxygen is released into the atmosphere and is a vital component for the survival of many organisms on Earth.

Option 4: Carbon dioxide is not a product of photosynthesis. Instead, it is one of the raw materials used by plants during photosynthesis. Plants absorb carbon dioxide from the atmosphere and use it to produce glucose and oxygen.

Therefore, the correct answer is Option 3: Oxygen.