This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
[{'content': 'Fatal hemoglobin has all the following characteristic features except \nSelect and explain. \nA. Strong affinity for 2, 3-DPG, B. Oxygen dissociation curve is shifted to left, C. At low fetal PO2 gives up more oxygen to tissues that adult haemoglobin, D. Forms 80% of haemoglobin at bih', 'role': 'user'}, {'content': "Answer: A \nExplanation: Fetal hemoglobin, or foetal haemoglobin, (also hemoglobin F, HbF, or a2g2) is the main oxygen transpo protein in the human fetus during the last seven months of development in the uterus and persists in the newborn until roughly 2-4 months old. Functionally, fetal hemoglobin differs most from adult hemoglobin in that it is able to bind oxygen with greater affinity than the adult form, giving the developing fetus better access to oxygen from the mother's bloodstream. In newborns, fetal hemoglobin is nearly completely replaced by adult hemoglobin by approximately 6 months postnatally, except in a few thalassemia cases in which there may be a delay in cessation of HbF production until 3-5 years of age. In adults, fetal hemoglobin production can be reactivated pharmacologically, which is useful in the treatment of diseases such as sickle-cell disease. Ref: guyton and hall textbook of medical physiology 12 edition page number: 310,311,312", 'role': 'assistant'}]