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': 'Which of the following is the most difficult impaction of a third molar? \nSelect and explain. \nA. Mesioangular impaction, B. Vertical impacted tooth, C. Partially impacted tooth, D. Distoangular impacted tooth', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]