This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Cholera prophylaxis is by - \nSelect and explain. \nA. Doxycycline 300mg OD, B. Cephalosporin, C. Streptomycin, D. Cotrimoxazole', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A single oral dose of doxycycline (300mg for adults and 6mg/kg for children under 15 years) has proved to be effective for chemoprophylaxis of cholera. Ref: PARK&;S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE 23rd edition , Page 233', 'role': 'assistant'}]