Here's the reasoning behind this order: (D) Pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out. Respiration begins with pulmonary ventilation (breathing), which allows the atmospheric air to enter the lungs and CO2-rich air to be exhaled. (A) Diffusion of gases (O2. and CO2) across the alveolar membrane. Inside the lungs, oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli across the alveolar membrane. (C) Transport of gases by the blood. Once in the bloodstream, oxygen and carbon dioxide are transported to and from the body's tissues. (B) Diffusion of O2 and CO2 between blood and tissues. Oxygen diffuses from the blood into the body's tissues, and carbon dioxide diffuses from the tissues into the blood. (E) Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2. Finally, oxygen is used by cells for metabolic processes, creating carbon dioxide as a byproduct.