Consider the Equilibrium Established in the Carbonic Acid-Bicarbonate Buffer System

Consider the equilibrium established in the carbonic acid-bicarbonate buffer system, which maintains pH balance in mammalian blood:
          H₂CO₃ → HCO ₃ ^- + H ⁺
During hypoventilation, breathing rate decreases, and therefore elimination of CO ₂ during exhalation decreases. How is optimal blood pH maintained when acid levels increase in our blood from hypoventilating? ​

A) excess H ⁺ from the acid react with H₂CO₃ to decrease pH level
B) excess H ⁺ from the acid react with H₂CO₃ to increase pH level
C) excess H ⁺ from the acid react with H₂CO₃ to maintain pH level
D) excess H ⁺ from the acid react with HCO ₃ ^- to increase pH level
E) excess H ⁺ from the acid react with HCO ₃ ^- to maintain pH level