question_answer

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.

A)  A-trachea - long tube supported by complete cartilaginous rings for conducting inspired air

B)  B-pleural membrane - surround ribs on both sides to provide cushion against rubbing.

C)  C-Alveoli - thin walled vascular bag like structures for exchange of gases.

D)  D-Lower end of lungs - diaphragm pulls it down during inspiration.