25.Which of the following statements BEST explains how increased CO₂ production contributes to the regulation of breathing rate?
(A) Increased CO₂ directly binds to hemoglobin, preventing oxygen transport and mechanically stimulating lung expansion to increase ventilation.
(B) CO₂ dissolves in plasma and is rapidly exhaled without chemical conversion, and breathing rate increases in response to decreased blood O₂ levels.
(C) Increased CO₂ is converted to carbonic acid by carbonic anhydrase in red blood cells. Carbonic acid dissociates leading to an increase in H+ concentration and a decrease in pH, which is detected by chemoreceptors.
(D) CO₂ produced during exercise remains primarily in gaseous form within tissues, directly activating stretch receptors in the lungs to increase breathing frequency.
(E) Elevated CO₂ suppresses respiratory center activity by stabilizing blood pH, thereby reducing the need for increased ventilation during exercise.