The number of oscillations that a wave completes per unit of time in called its

The number of oscillations that a wave completes per unit of time is called "frequency".
Frequency represents in fact how many complete cycles of the wave are done in a single unit of time. It can be written also as

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.