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': "Andrew's 5th key of occlusion is \nSelect and explain. \nA. Curve of spee, B. Rotation absent, C. Tight contacts, D. Bolton's ration", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]