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': 'Stress concentration in Root dentin is least with: \nSelect and explain. \nA. Smooth tapered post., B. Serrated tapered post, C. Smooth parallel post., D. Serrated parallel post', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]