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': 'In preparing an endodontically treated tooth for receiving a cast post, the minimal amount of gutta \npercha to be maintained for proper apical seal is \nSelect and explain. \nA. 1 mm, B. 8 mm, C. 4 mm, D. 0 mm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]