In certain people with lung disease, the partial pressure of oxygen in the pulmonary veins is lower than the partial pressure of oxygen in the alveoli. What might account for the difference in partial pressure of oxygen? 1. Many alveoli have collapsed, so there are not enough alveolar capillaries. 2. The partial pressure of oxygen in the pulmonary arteries is less than that in the alveolar air. 3. Oxygen diffuses from the alveolar air into the nearby alveolar capillaries too slowly.
- A1, 2 and 3
- B1 and 2 only
- C1 and 3 only
- D2 and 3 only