Mammalian lungs have enormous number of minute alveoli (air sacs). It is to allow

Options

A. More space for increasing the volume of inspired air
B. More surface area for diffusion of gases
C. More spongy texture for keeping lungs in proper shape
D. More nerve supply to keep organs active when working

Answer

b

Explanation

in mammalian lungs each alveolar duct ends in a passage , called atrium , which leads into a number of rounded alveolar sacs. Each alveolar sac is studded with a large number of air sacs or alveoli. Alveoli are the sites of respiration.