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: Social & Preventive Medicine
[{'content': 'The most infectious variety of diptheria is - \nSelect and explain. \nA. Anterior nasal diptheria, B. Posterior nasal diptheria, C. Faucial diptheria, D. Laryngeal diptheria', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]