A 2-Month- Boy Is Brought to the Office by His

A 2-month- boy is brought to the office by his mother because she has noticed that the baby is not feeding adequately. She received adequate prenatal care and admits to smoking one pack of cigarettes daily while pregnant. The boy's temperature is 36.3°C (97.3°F) , pulse is 171/min and respirations are 60/min. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination shows facial plethora. Capillary refill time is 3 seconds. The patient has a 4/6, harsh systolic, crescendo-decrescendo murmur best heard at the left upper sternal border. Laboratory studies show: Which of the following is the most likely explanation for this patient's elevated hematocrit?

A) Clonal proliferation of erythroid cells
B) Decreased pulmonary dead space
C) Impaired postnatal lung expansion
D) Increased blood flow to the renal arteries
E) Inflammation of the small airways
F) Underperfusion of the pulmonary arteries