This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
[{'content': 'Absence of dystrophin \nSelect and explain. \nA. DMD, B. Myotonic Dystrophy, C. Becker Dystrophy, D. Myasthenia Gravis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ref : harrisons 21st ed', 'role': 'assistant'}]