Answer : Option D

Explanation :

Human blood contains a buffer of carbonic acid (H₂CO₃) and bicarbonate anion (HCO₃^-) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid. Furthermore, the carbonic acid in the first equilibrium can decompose into CO₂ gas and water, resulting in a second equilibrium system between carbonic acid and water. Because CO₂ is an important component of the blood buffer, its regulation in the body, as well as that of O₂ , is extremely important. The effect of this can be important when the human body is subjected to strenuous conditions.

Source : chem.libretexts.org