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': 'Most common chromosomal syndrome is- \nSelect and explain. \nA. Fragile X syndrome, B. Trisomy 17, C. Trisomy 21, D. Trisomy 13', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Down syndrome or trisomy 21 is the most common chromosomal anomaly.', 'role': 'assistant'}]