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: Medicine
[{'content': "All are true about perinatal transmission of HIV Except- \nSelect and explain. \nA. Cannot be diagnosed by routine confirmatory test., B. Post natal transmission is not possible., C. Infant transmission rate is <50%, D. Virus can be isolated from mother's milk", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]