Question

how is the majority of carbon dioxide carried in the blood?
o combined with hemoglobin
o as co₂ dissolved in the plasma
o as bicarbonate ion in the blood plasma
o in the cytoplasm of red blood cells
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Explanation:

Carbon dioxide is transported in the blood in three forms: dissolved in plasma (about 7%), combined with hemoglobin (about 23%), and as bicarbonate ions ($HCO_3^-$) (about 70%). The majority is in the form of bicarbonate ions. This is because when $CO_2$ enters red blood cells, it reacts with water ($H_2O$) in the presence of carbonic anhydrase to form carbonic acid ($H_2CO_3$), which then dissociates into $H^+$ and $HCO_3^-$. The $HCO_3^-$ then diffuses into the plasma.

Answer:

as bicarbonate ion in the blood plasma