Which of the following is an example of a controlled experiment?
-an experiment where there are many uncontrolled variables
- an experiment where there is only one variable
- an experiment where there are no variables

Examples: mental health problems cardiovascular disease obesity and other eating disordersmenstrual problems skin and hair problems

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.