Answer:
b. diffusion.
Step-by-step explanation:
Diffusion can be defined as the movement of gas molecules from a region of high concentration to a region of lower concentration until an equilibrium is attained or reached. This mixing of gas molecules in the liquid or gaseous state is due to their kinetic energy of random motion i.e without requiring bulk motion.
This ultimately implies that, diffusion is a phenomenon through which gas molecules in either a gaseous or liquid state spread out in response to a concentration gradient, which is simply the difference in concentration of the gases across a space.
During diffusion, molecules move from areas of high concentration to areas of low concentration.
In this context, the process by which dissolved gases are exchanged between the blood and interstitial fluids is referred to as diffusion.
On a related note, this process is also referred to as internal respiration because it involves the exchange of oxygen gas and carbon (II) oxide gas between tissue cell and capillaries.