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

Options

A. D – Lower end of lungs – diaphragm pulls it down during inspiration
B. A – Trachea – long tube supported by complete cartilaginous rings for conducting inspired air
C. B – Pleural membrane – surrounds ribs on both sides to provide a cushion against rubbing
D. C – Alveoli – thin-walled vascular bag-like structures for the exchange of gases

Answer

D

Explanation

In the given figure A is the trachea. It is supported by incomplete cartilaginous rings which prevent its collapse during inspiration B is the pleural membrane. It encloses lungs, C are alveoli. They are thin-walled sacs hawing extensive network of capillaries for gaseous exchange D is the diaphragm.