The exchange of gases between the blood capillaries and the alveoli of the lungs occurs by
The correct option is D simple diffusion
The exchange of gases (oxygen and carbon dioxide) occurs between the alveoli and blood capillaries by simple diffusion. This naturally occurs according to the partial pressure gradients of the respective gases. Oxygen from the alveoli diffuses into the blood, while carbon dioxide from the blood diffuses into the alveoli.