The figure below shows the simplified diagram of the insect respiratory system that we used to model its supply of oxygen to its cells via diffusion.

Why did we have to divide the entire length that an oxygen molecule has to traverse via diffusion from the external atmosphere to inside the mitochondria of a body cell into two distances, and calculate the rate of diffusion separately for the distance X-Y and Y-Z?

Select one:

a. oxygen is moved via bulk flow through one, and via diffusion through the other distance

b. the distances X-Y and Y-Z are of very different lengths

c. (P2-P1) differs between the two distances

d. k differs for the two distances

e. A differs between the two distances

Answer B is not correct