What of the following factors cause a reduction in the pulmonary vascular resistance following the first breath?

I. Increased alveolar pressure of oxygen
II. Removal of lung fluid which reduces pressure on pulmonary vessels
III. Increase in lung volumewhich widens the caliber of extralveolar vessels

a. I, II, and III c. I only
b. II and III only d. I and II only

a. I, II, and III