The total thickness of the diffusion membrane of alveolus capillary is
a)	Less than 1 cm	b)	Less than 2 cm	c)	Less than 1 mm	d)	More than 1 mm

(c)

The total thickness of the diffusion membrane is less than 1 milimeter.

The diffusion membrane is made up of three major layers (figure) namely, the thin squamous epithelium of alveoli, the endothelium of alveolar capillaries and the basement substance in between them. However, its total thickness is much less than a millimeter. Therefore, all the factors in our body are favourable for the diffusion of  from alveoli to tissues and that of  from the tissues to alveoli