The total mass of A and C which are glucose and oxygen, is equal to the total mass of B and D, which are water and Carbon dioxide.
the law of conservation states that no energy or matter should be lost during a reaction therefore total masses should be equal so you're looking to 2 numbers that equal each other when added and the only 2 are A and C equal B and D
In respiration we know that the waste products are water vapor (H2O) and carbon dioxide. Which makes the last statement correct.
