Final answer:
Pulmonary edema, emphysema, and hyperventilation can result in a decreased PO2 in arterial blood.
Step-by-step explanation:
In arterial blood, a decreased PO2 can result from both pulmonary edema and emphysema. Pulmonary edema refers to the accumulation of fluid in the lungs, which can disrupt the exchange of oxygen and carbon dioxide in the alveoli. Emphysema involves the destruction of the alveolar walls, reducing the surface area available for gas exchange.
Hyperventilation, on the other hand, can actually result in an increased PO2 in arterial blood due to the increased removal of carbon dioxide and subsequent increase in blood pH.
Therefore, the correct answer is d) Answers a and b are correct.