This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hemolytic anemia, Subject name: Pediatrics
[{'content': "Ba's hydrops fetalis is lethal because: \nSelect and explain. \nA. Hb Ba's cannot bind oxygen, B. The excess a-globin form insoluble precipitates, C. Hb Ba's cannot release oxygen to fetal tissues, D. Microcytic red cells become trapped in the placental", 'role': 'user'}, {'content': "Answer: C \nExplanation: Hb Ba: Most severe form of Alpha thalassemia As Hb Ba's consists of 4-gamma chains - have very high oxygen affinity Thus, it cannot release oxygen to fetal tissues.", 'role': 'assistant'}]