This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': "Features of carotid-cavernous fistula include \nSelect and explain. \nA. Dilated superior ophthalmic vein on CT scan, B. Blood in the Schlemm's canal, C. Proptosis of contralateral eye suggests bilateral carotid-cavernous fistula, D. Traumatic fistula rarely close spontaneously", 'role': 'user'}, {'content': 'Answer: C \nExplanation: * With anterior drainage through orbit carotid cavernous fistula produce proptosis, diplopia, glaucoma and corkscrew, aerialized conjunctival vessels carotid-cavernous fistula results from an abnormal communication between the aerial and venous systems within the cavernous sinus in the skull. It is a type of aeriovenous fistula Ref Harrison20th edition pg 2567', 'role': 'assistant'}]