Think about the movements of players in a baseball game. Some walk up to bat. Others sprint to steal a base. An outfielder jogs back to position after catching a fly ball. The catcher squats, staying as still as he can. How could you describe each player’s speed?

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.