In order for oxygen to diffuse from the alveoli into the capillaries, the partial pressure of the oxygen in the alveoli in the lungs must be:
a. the same pressure between both the lungs and the capillaries
b. oxygen cannot diffuse through the alveoli
c. higher in the lungs than in the capillaries
d. higher in the capillaries than in the lungs

The correct answer will be option-C

Explanation:

In an organism, the mechanism of gas exchange depends on the partial pressure and total pressure of the gas.  Partial pressure is the pressure of the gas exerted by a single type of gas in a mixture of gases and this pressure determines the movement of gases in the system.

The diffusion of the oxygen from the alveoli to blood capillaries depends on the partial pressure as the partial pressure of oxygen is high in alveoli measured about 104 mmHg compared to the capillaries measured about 40 mmHg.

This difference in the pressure generates pressure gradient which leads to the movement of the oxygen from alveoli to the capillaries as the movement takes place from higher to lower concentration gradient.

Thus, Option-C is the correct answer.