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 maxillary tooth that is difficult to anaesthetize by infiltration is: \nSelect and explain. \nA. Canine, B. 3rd molar, C. Incisors, D. 1st molar', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The maxillary tooth that is difficult to anaesthetize by infiltration is First molar due to the presence of thick zygomatic buttress in this region.', 'role': 'assistant'}]