The figure shows a diagrammatic view of human respiratory system with labels A, B, C and D . Select the option, which gives correct identification and main function and/or characteristic.

Step-by-step solution

C-Alveoli are thin-walled vascular bag-like structures for exchange of gases. A-trachea or wind pipe is an air conducting tube through, which transport of gases takes place. B-pleural membrane is double layered, which reduces friction on the lung surface. D-diaphragm is involved in the inspiration and expiration process of breathing.