Division of mammalian lungs into a very large number of tiny alveoli around alveolar ducts opening into brondchioles, is

Options

A. An inefficient system of ventilation of alveoli though with very little residual air
B. An inefficient system of ventilating the alveoli resulting in a very high percentage of residual air in the lungs
C. A very efficient system of ventilating the alveoli with no residual air
D. An efficient system of ventilation of alveoli with little or no residual air

Answer

D

Explanation

Mammalian lung has a small sac-like structure called alveoli which helps in gaseous exchange. After a forcible exhalation, the volume of air remains in the lungs is called residual air so the lungs do not collapse.