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': 'A convalescent case of cholera remains infective for \nSelect and explain. \nA. 14-21 days, B. 7-14 days, C. < 7 days, D. 21-28 days', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Types of carriers in Cholera:', 'role': 'assistant'}]