Which of the Following Situations Related to Transition from Fetal

Which of the following situations related to transition from fetal to perinatal circulation would be most likely to necessitate medical intervention?

A) Pressure in pulmonary circulation and the right side of the infant's heart fall markedly.
B) Alveolar oxygen tension increases causing reversal of pulmonary vasoconstriction of the fetal arteries.
C) Systemic vascular resistance and left ventricular pressure are both increasing.
D) Pulmonary vascular resistance, related to muscle regression in the pulmonary arteries, rises over the course of the infant's first week.