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: Dental
[{'content': 'The model of web of causation of diseases was first suggested by: \nSelect and explain. \nA. Pettenkofer, B. Mac Mohan & Pugh, C. John M. Last, D. C.E.A. Winslow', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]