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 patient presented with unilateral proptosis, which was compressible and increases on ending forward. No thrill or bruit was present. MRI shows a retro-orbital mass with enhancement. The likely diagnosis is: \nSelect and explain. \nA. AV malformations, B. Orbital encephalocoecle, C. Orbital varix, D. Neurofibromatosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Orbital varix', 'role': 'assistant'}]