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': 'A patient who was previously with good muscle mass now presents with decreased muscle mass. There is a history of RTA which led him to be bedridden for 6 months. This decrease in muscle mass is best explained by \nSelect and explain. \nA. Metaplasia, B. Dysplasia, C. Hypertrophy, D. Atrophy', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]