| (A) | Diffusion of gases (O2 and CO2) across alveolar membrane |
| (B) | Diffusion of O2 and CO2 between blood and tissues |
| (C) | Transport of gases by the blood |
| (D) | Pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out |
| (E) | Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2 |
| 1. | (D), (A), (C), (B), (E) | 2. | (C), (B), (A), (E), (D) |
| 3. | (B), (C), (E), (D), (A) | 4. | (A), (C), (B), (E), (D) |
| 1. | Provides surface for diffusion of O2 and CO2 |
| 2. | It clears inhaled air from foreign particles |
| 3. | Inhaled air is humidified |
| 4. | Temperature of inhaled air is brought to body temperature |