This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Orbit and Adnexa, Subject name: Ophthalmology
[{'content': 'Cause of pulsating proptosis \nSelect and explain. \nA. Lymphoma, B. Caroticocavernous fistula, C. Orbital cellulitis, D. Mucocele of paranasal sinuses', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Causes of Pulsatile Proptosis Caroticocavernous fistula Aneurysms of Ophthalmic aery Transmitted cerebral pulsation from deficient orbital roof like congenital meningocele / meningo-encephalocele', 'role': 'assistant'}]