Question

a patient has severe pneumonia, which has thickened the respiratory membrane. despite oxygen therapy, he still has rapid respiration and feels as if he is not getting enough air. this is because
multiple choice
the o₂ stimulates the respiratory center to increase the respiratory rate.
his blood ph increased and stimulated an increase in his respiratory rate.
the o₂ increases the stimulation of the carotid and aortic bodies.
even though he is receiving enough o₂, co₂ and h⁺ accumulate in his blood and cause the respiratory rate to continue to increase.
o₂ cannot diffuse across the thickened membrane.

Explanation:

The thickened respiratory membrane due to severe pneumonia impedes the normal diffusion of oxygen ($O_2$). Oxygen therapy may provide $O_2$, but if it cannot diffuse across the thickened membrane, the patient will still feel short - of - breath and have a rapid respiratory rate. The other options do not directly address the core issue of oxygen not being able to diffuse properly across the thickened membrane.

Answer:

O₂ cannot diffuse across the thickened membrane.