This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
[{'content': "Bart's hydrops fetalis is lethal because \nSelect and explain. \nA. Hb Bart's cannot bind oxygen, B. Hb Bart's cannot release oxygen to fetal tissues, C. Microcytic red cells become trapped in the placental, D. The excess a - globin form insoluble precipitates", 'role': 'user'}, {'content': "Answer: B \nExplanation: Bart hydrops fetalis is a lethal complication of alpha thalassemia trait where oxygen can't release from hemoglobin", 'role': 'assistant'}]