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: Ophthalmology
[{'content': 'A most common cause of posterior staphyloma – \nSelect and explain. \nA. Trauma, B. Glaucoma, C. Myopia, D. Scleritis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Degenerative high axial myopia is the most common cause of posterior staphyloma.', 'role': 'assistant'}]