Why Is the Pharmacological Reactivation of Fetal Hemoglobin in a Patient

Why is the pharmacological reactivation of fetal hemoglobin in a patient with sickle cell anemia often a successful treatment?

A) Fetal hemoglobin binds more oxygen molecules than adult hemoglobin.
B) Fetal hemoglobin is better able to release oxygen than is adult hemoglobin.
C) Fetal hemoglobin has a higher affinity for oxygen than does adult hemoglobin.
D) Fetal hemoglobin is better able to release carbon dioxide than is adult hemoglobin.
E) Fetal hemoglobin has a higher affinity for carbon dioxide than does adult hemoglobin.