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: Pathology
[{'content': 'A case presenting with a gray coloured pseudomembrane\nwhose removal is difficult and painful, can be \nSelect and explain. \nA. ANUG, B. Diphtheritic lesion, C. Secondary stage of syphilis, D. Desquamative gingivitis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]