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: Medicine
[{'content': 'Carotid atheromas may appear radiographically as: \nSelect and explain. \nA. Nodular radio-opaque mass, B. Double vertical radio-opaque lines within the neck, C. Both of the above, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]