There are many important laws and theories in science. Which of the following is a law of science? A. A living thing is made of at least one cell.
B. An atom is made of electrons orbiting a nucleus.
C. Gravity will pull two objects toward each other.
D. Natural selection will change species to fit their environments.

Ido not know at all

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.