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': 'Identification of cholera by Snow is an example of? \nSelect and explain. \nA. Spot map, B. Random trial, C. Analytical design, D. Experimental design', 'role': 'user'}, {'content': 'Answer: A \nExplanation: <p> John Snow of England in his classic investigation of cholera epidemic in 1854 is an example of spot map. Park&;s textbook of preventive and social medicine,K.Park,23rd edition,page no:66 <\\p>', 'role': 'assistant'}]