Answer the following question given this paragraph: 

Recall that the only required ingredients needed for photosynthesis are sunlight, carbon dioxide (CO 2 ), and water (H 2 O). From these simple inorganic ingredients, photosynthetic organisms produce the carbohydrate glucose (C 6 H 12 O 6 ), and other complex organic compounds. Essentially, these producers are changing the energy from the sunlight into a usable form of energy. They are also making the oxygen that we breathe. Oxygen is a waste product of photosynthesis.


Q: For photosynthesis to begin, the inputs required are sunlight, water, and what?


A:
carbon dioxide