This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concept of health and disease, Subject name: Social & Preventive Medicine
Which events occured before 1900 AD? 
Select and explain. 
A. Establishment of seat of social medicine at Oxford, B. Epidemiological work on cholera by John Snow, C. Work on scurvy by James Lind, D. Use of BCG vaccine
B: Epidemiological work on cholera by John Snow
Answer: B: Epidemiological work on cholera by John Snow 
Explanation: An english epidemiologist John Snow studied the epidemiology of cholera in London from 1848-1854 and established the role of polluted drinking water in spread of cholera. Ref : Park&;s textbook of preventive and social medicine; 23rd edition