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: ENT
[{'content': 'A patient has carcinoma of right tongue on its lateral border of anterior 2/3rd, with lymph node of size 4 cm in level 3 on left side of the neck, stage of disease is: \nSelect and explain. \nA. NO, B. N1, C. N2, D. N3', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Classification of stage of tumor of oral cavity based on size of lymph node.', 'role': 'assistant'}]