Polycythemia Occurs in a Fetus Because

Polycythemia occurs in a fetus because:

A) fetal hemoglobin has a greater affinity for oxygen due to DPG.
B) the fetus has a different hemoglobin structure of two α- and two γ-chains rather than two α-and two β-chains.
C) there is increased erythropoiesis in response to the hypoxic intrauterine environment.
D) the lungs of the fetus are undeveloped and unable to adequately diffuse oxygen to the pulmonary capillaries.