Answer:
blood
Step-by-step explanation:
Alveoli are microscopic spaces of the lung where oxygen is exchanged for carbon dioxide, at the end of the bronchi; Each lung has millions of alveoli.
The Pulmonary Alveoli are the places where hematosis or gas exchange between the blood and the lungs is performed, that is, it is an exchange of gases and not of blood. Hematosis is the exchange of gases between the lung and the blood that is produced by osmosis at the level of the alveolar sacs of each lung. In this process, CO2 passes from the arterial capillaries into the alveolar sac and O2 from the alveolar sac to the Venous capillaries producing decarboxylation and oxygenation of the blood. This gas exchange is produced by a simple difference in pressure and concentration called diffusion (from where there is more to where there is less), and implies a phenomenon of passive diffusion.