Which of the following properties of alveoli is/are helpful in gaseous exchange during respiration in human beings? I. The epithelial lining of alveoli is very thin. II. Elastic fibres are present in alveolar wall. III. Wall of alveoli is surrounded by many blood capillaries. Select the correct answer using the code given below.

Step-by-step solution

Gaseous exchange in the alveoli occurs primarily through simple diffusion. A very thin epithelial lining of the alveoli minimizes the diffusion distance for gases, which significantly increases the rate of gaseous exchange. Thus, statement I is correct. The presence of a dense network of blood capillaries surrounding the alveolar walls continuously removes oxygen and brings carbon dioxide. This maintains a steep concentration gradient essential for efficient diffusion. Thus, statement III is correct. Although elast