The number remains unchanged during photosynthesis is the number of carbon atoms.
Photosynthesis is a term to refer to the conversion of inorganic matter to organic matter thanks to the energy provided by sunlight.
This transformation is expressed in the following chemical function
6CO2 + 6H2O --sunlight -> C6H12O6 + 6O2.
As evidenced in the chemical function, the number of carbon atoms does not change because at the beginning and end of the reaction there are 6 carbons. However, other molecules such as water, glucose or carbon dioxide change as they degradate or combine with others.
Therefore, the correct answer is D. while options A, B and C are incorrect because they refer to elements that do change their number during this function.
Learn more in: https://brainly.com/question/797243
