| I: | Haemoglobin in humans adapted to very high altitudes has a lower binding affinity for oxygen than that found in humans living at the sea level. |
| II: | Lower affinity of haemoglobin to oxygen means more oxygen can bind to haemoglobin even at low partial pressures |
| 1. | Both I and II are correct and II explains I |
| 2. | Both I and II are correct but II does not explain I |
| 3. | I is correct but II is incorrect |
| 4. | Both I and II are incorrect |