For efficient gaseous exchange to take place in the human lungs, steep concentration gradients must be kept in place. Which row shows correctly how steep concentration gradients can be maintained?
- AElastic fibres in the walls of the alveoli recoil when breathing out: ✓ ; Continual supply of deoxygenated blood by the pulmonary artery: ✓
- BElastic fibres in the walls of the alveoli recoil when breathing out: ✗ ; Continual supply of deoxygenated blood by the pulmonary artery: ✓
- CElastic fibres in the walls of the alveoli recoil when breathing out: ✓ ; Continual supply of deoxygenated blood by the pulmonary artery: ✗
- DElastic fibres in the walls of the alveoli recoil when breathing out: ✗ ; Continual supply of deoxygenated blood by the pulmonary artery: ✗