Diffusion of respiratory gases is inversely proportional to:

Explanation

Explanation: 1. Surface area (Option a): Diffusion of respiratory gases is directly proportional to the surface area available for gas exchange. The larger the surface area, the more space there is for gas molecules to pass through, which enhances the efficiency of gas exchange. This is why the lungs have a large number of tiny alveoli to maximize the surface area for gas exchange. 2. Thickness of the membrane (Option b): Diffusion of respiratory gases is inversely proportional to the thickness of the membrane through which the gases need to pass. A thinner membrane allows gases to diffuse more rapidly, whereas a thicker membrane creates more resistance and slows down the diffusion process. In the respiratory system, the alveolar-capillary membrane is very thin to facilitate efficient gas exchange. 3. Difference in concentration (Option c): Diffusion of respiratory gases is directly proportional to the difference in concentration of the gases on either side of the exchange surface. This difference in concentration drives the movement of gases from an area of higher concentration to an area of lower concentration until equilibrium is reached. 4. Presence of moisture (Option d): The presence of moisture does not directly affect the rate of diffusion of respiratory gases. However, moisture in the respiratory system is essential for keeping the exchange surfaces, such as the alveoli, moist and allowing gases to dissolve for efficient exchange. The presence of moisture prevents the exchange surfaces from drying out and aids in maintaining a favorable environment for gas exchange.