Answer:C) Total number of carbon, hydrogen, and oxygen atoms in glucose and oxygen.
Explanation: During cellular respiration, one molecule of glucose is broken down in the presence of six molecules of oxygen to produce six molecules of carbon dioxide, six molecules of water and energy.
The equation for the reaction is C6H12O6+ 6O2 --> 6CO2 + 6H2O + Energy.
In writing a balanced chemical equation, the mass of the products formed in the reaction must be equal to the mass of the reactants at the beginning of the reaction. This is because according to the law of conservation of mass, matter can neither be created nor be destroyed in an ordinary chemical reaction. This means that the total number of carbon, hydrogen and oxygen atoms in glucose and oxygen molecules (the reactants) must be equal to the total number of carbon, hydrogen and oxygen atoms in carbon dioxide and water (the products) formed.