If Anything Decreases Alveolar PO₂,how Does That Affect the Alveolar-Blood

Multiple Choice

If anything decreases alveolar PO₂,how does that affect the alveolar-blood oxygen pressure gradient?

A) Anything that decreases alveolar PO2 tends to increase the alveolar-blood oxygen pressure gradient and, therefore, tends to increase the amount of oxygen entering the blood.
B) Anything that decreases alveolar PO2 tends to decrease the alveolar-blood oxygen pressure gradient and, therefore, tends to decrease the amount of oxygen entering the blood.
C) Anything that decreases alveolar PO2 tends to increase the alveolar-blood diffusion rate and, therefore, tends to increase the amount of oxygen entering the blood.
D) Anything that decreases PO2 tends to increase arterial-blood PO2 and, therefore, tends to decrease the amount of oxygen entering the blood.