Multiple choice Which one does not contribute to the reproduction of CO2? Respiration Decomposition of organic wastes Burning of fossil fuels Birds excreta Reveal answer Fill a bubble to check yourself D Correct answer Explanation Some amount of phosphorus is returned to the earth, in the form of bird's excreta - Guano deposits (excreta of marine birds) and dead fish (around 60,000 tonnes which is less than 0.5% of phosphorus discharged from rivers)