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: Surgery
[{'content': 'The "red line" in winter\'s classification of impacted teeth represents: \nSelect and explain. \nA. The depth at which the impacted teeth is located, B. The angulation of the 2nd molar, C. The summit of the alveolar bone covering the impacted tooth, D. Relation of the 3rd molar to the ramus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]