This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharynx, Subject name: ENT
[{'content': 'Pseudomembrane over tonsil and pharynx is caused by \nSelect and explain. \nA. Gram positive bacili, B. Gram negative bacili, C. SS RNA virus, D. Catalase negative cocci', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pseudomembrane is formed in diphtheria, which is caused by Corynebacterium diphtheria, which is a gram-positive bacillus Ref: Harshmohan textbook of pathology; 7th edition', 'role': 'assistant'}]