Which of the following is an evidence of photosynthesis?

The evidence of photosynthesis is the formation of starch. Starch is a complex carbohydrate that is synthesized by plants during the process of photosynthesis. The energy for this process is obtained from the absorption of light by pigments such as chlorophyll. Carbon dioxide from the air and water from the soil are also necessary for photosynthesis to occur. During photosynthesis, water molecules are split into hydrogen and oxygen, but this process is not considered as direct evidence of photosynthesis. Therefore, the correct answer is the formation of starch.