The diagrammatic representation shows the pulmonary and systemic circulations. Identify the parts labelled as a, b, c, and d and select the correct option.
| a | b | c | d | |
| A | Pulmonary vein | Vena cava | Aorta | Pulmonary artery |
| B | Pulmonary vein | Vein | Pulmonary artery | Aorta |
| C | Vena cava | Pulmonary artery | Pulmonary vein | Aorta |
| D | Aorta | Vein | Pulmonary vein | Pulmonary artery |