Breathing rate is adjusted moment to moment by chemical signals reaching the medulla, not by mechanical stretch alone. Evaluate the following Assertion and Reason on how CO₂ levels drive this regulation.

• Assertion (A): A rise in the CO₂ concentration of blood changes the rate and depth of breathing far more strongly than a comparable fall in O₂ concentration.
• Reason (R): A chemosensitive area adjacent to the rhythm centre in the medulla, together with receptors associated with the aortic arch and carotid artery, is highly sensitive to CO₂ and H⁺ concentration and signals the rhythm centre to make the necessary adjustments.