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': 'Incubation period of chancroid is \nSelect and explain. \nA. Less than 7 days, B. 10-15 days, C. 2-3 weeks, D. 3-4 weeks', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]