Photosynthesis is the process through which plants produce sugar and oxygen. Photosynthesis can also take place in single-celled organisms like phytoplankton and other microorganisms. The process of photosynthesis occurs differently from one organism to the next, but several features remain the same. In short, photosynthesis takes in water and carbon dioxide, uses sunlight as a catalyst, and produces oxygen and sugar. The plants release the oxygen through respiration. They digest or store the sugar.
Although the process seems simple, it is the most important event on the planet as far as animal life is concerned. Oxygen is a byproduct of photosynthesis. Animals would not be able to breathe if it was not for this process. Herbivores live off these fruits and vegetables and form the basis of any food chain. Carnivores and omnivores would not be able to find food if it were not for these sugars. Were it not for the simple process of photosynthesis, the Earth would be an uninhabited planet.

Animals would not be able to breathe if it was not for this process.
How does this sentence help to develop the idea that photosynthesis is essential to animal life?

A. It shows that animals depend on this process for oxygen.
B. It suggests that photosynthesis occurs in all animals.
C. It suggests that photosynthesis takes place in the lungs.
D. It shows that animals depend on this process for food.