In humans, respiration occurs in the following steps. Arrange these...

The steps of respiration in humans occur in the following sequence:

First, pulmonary ventilation (breathing) takes place, by which atmospheric air is drawn in and $\text{CO}_2$ rich alveolar air is released out (C).

Second, diffusion of gases ($\text{O}_2$ and $\text{CO}_2$) occurs across the alveolar membrane (B).

Third, transport of gases is carried out by the blood (E).

Fourth, diffusion of $\text{O}_2$ and $\text{CO}_2$ takes place between the blood and tissues (A).

Finally, cellular respiration occurs, where $\text{O}_2$ is utilised by the cells for catabolic reactions and $\text{CO}_2$ is released (D).

The correct sequence is C, B, E, A, D.

Answer: C, B, E, A, D