Select the favourable conditions required for the formation of oxyhaemoglobin at the alveoli.

The correct answer is: High pO₂, low pCO₂, less H⁺, lower temperature

Step-by-Step Explanation:
Oxyhaemoglobin is formed when oxygen binds to haemoglobin. This association of oxygen with haemoglobin is highly reversible and depends primarily on the partial pressure of oxygen (${\mathrm{pO}}_2$).

In the alveoli of the lungs, several factors act together to promote the association of oxygen with haemoglobin:
1. High ${\mathrm{pO}}_2$: The oxygen concentration in the alveolar air is high, which encourages oxygen molecules to bind to haemoglobin.
2. Low ${\mathrm{pCO}}_2$: Carbon dioxide is actively cleared from the blood into the alveoli, resulting in low partial pressure of carbon dioxide in the vicinity.
3. Less $H^{+}$ concentration (Higher pH): Lower levels of acidity (less hydrogen ion concentration) stabilize the structure of haemoglobin in a state that has a high affinity for oxygen.
4. Lower temperature: Lower metabolic activity and heat generation in the lungs compared to active tissues keep the temperature relatively lower, which further stabilises the oxyhaemoglobin complex.

In contrast, in the tissues, low ${\mathrm{pO}}_2$, high ${\mathrm{pCO}}_2$, high $H^{+}$ concentration (lower pH), and higher temperature are found, which favour the dissociation of oxygen from oxyhaemoglobin.
Therefore, the alveoli provide the ideal conditions for oxyhaemoglobin formation: high ${\mathrm{pO}}_2$, low ${\mathrm{pCO}}_2$, less $H^{+}$, and lower temperature.