This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of orbit, Lids and lacrimal apparatus, Subject name: Ophthalmology
[{'content': 'Pulsatile proptosis is a feature of- \nSelect and explain. \nA. orbital varix, B. Retinoblastoma, C. Coico - cavernous fistula, D. Covernous sinus thrombosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: *Coicocavernous fistula causes pulsatile proptosis. Ref: Clinical ophthalmology 2nd/e p.786', 'role': 'assistant'}]