During respiration carbon dioxide and water are combined to make glucose oxygen and water are combined to make glucose carbon dioxide is used to break down glucose into energy oxygen is used to break down glucose into energy

-Oxygen is used to break down glucose into energy.

Explanation:

Cellular respiration involves breakdown of organic molecules, such as glucose to release energy. Cells use oxygen to breakdown glucose molecules to release energy in the form of ATP molecules, along with water and carbon dioxide.

It is divided into three steps, glycolysis, Krebs cycle, and electron transport chain. By one glucose molecule, a total of 36 ATP molecules are produced during cellular respiration, which are used as energy currencies of the cell.  

Thus, the correct answer is 'last option.'

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