Answer:
Carbon Dioxide
Explanation:
According to my research on the respiratory system, I can say that based on the information provided within the question Bicarbonate ions are converted into Carbon Dioxide at the alveolus. Oxygen is transported by the lungs into the bloodstream which later end up in many tiny air sacs of the lungs known as the alveolus which allow for rapid gaseous exchange that change the oxygen into carbon dioxide to later be exhaled.
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