Neco 2023 Biology Question 25

A mountain goat lives at an altitude of \(3000\ \text{m}\) where the atmospheric pressure is \(70\ \text{kPa}\) (sea‑level pressure \(101.3\ \text{kPa}\)). The partial pressure of oxygen (\(P_{O_2}\)) is \(21\%\) of the atmospheric pressure. At sea level the goat's hemoglobin has a \(P_{50}\) of \(26\ \text{mmHg}\) and the Hill coefficient \(n = 2.5\). At altitude the goat shows two physiological adjustments: (i) ventilation increases to \(1.8\) times the sea‑level value, and (ii) the hemoglobin's affinity for O\(_2\) increases so that \(P_{50}\) falls to \(22\ \text{mmHg}\). Assuming arterial oxygen saturation (\(S_{aO_2}\)) is given by the Hill equation \[S_{aO_2}= \frac{P_{O_2}^{\,n}}{P_{50}^{\,n}+P_{O_2}^{\,n}}\] with \(n = 2.5\), and that arterial oxygen content is proportional to \(S_{aO_2}\), which of the two adjustments contributes more to the relative increase in arterial oxygen saturation compared with the sea‑level condition? Answer "ventilation" or "hemoglobin affinity".