This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Pediatrics
[{'content': "Bart's hydrops fetalis is lethal because: \nSelect and explain. \nA. Hb Bart's cannot bind oxygen, B. The excess a-globin form insoluble precipitates, C. Hb Bart's cannot release oxygen to fetal tissues, D. Microcytic red cells become trapped in the placental", 'role': 'user'}, {'content': "Answer: C \nExplanation: c. Hb Bart's cannot release oxygen to fetal tissues(Ref: Nelson's 20/e p 2349-2352, Ghai 8/e p 341)As Hb Bart's consists of 4y chains, which have very high oxygen affinity, it cannot release oxygen to fetal tissues.", 'role': 'assistant'}]