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': 'Most common primary tumor of orbital cavity presenting as proptosis is \nSelect and explain. \nA. Cavernous hemangioma, B. Retinoblastoma, C. Malignant melanoma, D. Uveal melanoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]