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
Concept of Web of causation was proposed by: 
Select and explain. 
A. McMohan and Pugh, B. Louis Pasteur, C. John Snow, D. John Snow
A: McMohan and Pugh
Answer: A: McMohan and Pugh 
Explanation: McMohan and Pugh