12. What function SPECIFICALLY causes oxygen to diffuse into blood, and CO2 to diffuse
into alveoli?
A. Blood carries oxygen to the lungs and CO2 away from the lungs.
B. Air in the alveoli has a greater concentration of oxygen, and lower concentration of CO2
than the blood in the lungs.
C. Blood passes into capillaries that supply body cells with oxygen, and pick up CO2 as cell
waste.
D. The heart pumps blood to the lungs