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: Pathology
[{'content': 'Patau syndrome due to - \nSelect and explain. \nA. Trisomy 21, B. Trisomy 13, C. 18 P, D. Trisomy 18', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]