| A. | Diffusion of gases across alveolar membrane |
| B. | Diffusion of gases between blood and tissues |
| C. | Transport of gases by blood |
| D. | Utilisation of \(O_2\) by the cells for catabolic reactions |
| E. | Breathing or pulmonary ventilation |
| 1. | A →E→B→C→D | 2. | C →E→A→B→D |
| 3. | B →D→C→E→A | 4. | E →A→C→B→D |