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': "In which of the following trinucleotide repeat mutation occurs in coding regions of DNA? \nSelect and explain. \nA. Myotonic dystrophy, B. Huntington's disease, C. Fragile x syndrome, D. Friedeich ataxia", 'role': 'user'}, {'content': "Answer: B \nExplanation: In\xa0Huntington's disease CAG repeat mutation occurs in coding regions of DNA.", 'role': 'assistant'}]