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': 'Most common source of infection for whooping cough- \nSelect and explain. \nA. Chronic carrier, B. Acute carrier, C. Case, D. Convelescent carrier', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]