How often should cardio exercises be performed? A. Never B. Three to five times a month C. Three to five times a week D. Three to five times a day

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.

Ithink it is a. but i'm not 100 percent sure.