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': "A chromosomal anomaly associated with alzheimer's dementia is - \nSelect and explain. \nA. Trisomy 18, B. Patau syndrome, C. Trisomy 21, D. Turners syndrome", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]