In our basic metabolic paradigm, we take in oxygen and breathe out carbon dioxide as a metabolic product. Carbon dioxide is a gaseous waste product that results out of cellular respiration that occurs within mitochondria. In the blood, more than 90% of the carbon dioxide exists as bicarbonate.
It is a fact that carbon dioxide is not carried in solution within the blood. Nor is it bound to blood proteins.
Carbon dioxide is not carried on hemoglobin. Instead, oxygen is carried on hemoglobin. Hemoglobin is a protein present in large numbers within the red blood cells.
Carbon dioxide is not converted to bicarbonate in the plasma. (Plasma is the colorless fluid part of the blood, devoid of the red blood cells.)
Therefore, options A, B & D are incorrect.
Oxygen-carbon dioxide transfers are intricately woven networks within the red blood cells and this process is mediated by the enzyme carbonic anhydrase. This enzyme is one of the most efficient enzymes known!
Therefore, option (C) is correct.