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': 'Patient with head and neck cancer with contralateral Lymphnode of 3 cm size. Nstaging \nSelect and explain. \nA. N2a, B. N2b, C. N2c, D. N3', 'role': 'user'}, {'content': 'Answer: C \nExplanation: N0\nNo nodal metastasis\n\xa0\n\xa0\n\n\nN1\nSingle\nIpsilateral\nEqual to or <3 cm\n\n\nN2a\nSingle\nIpsilateral\n3 to 6 cm\n\n\nN2b\nMultiple\nIpsilateral\nNone > 6 cm\n\n\nN2c\nSingle or Multiple\nBilateral or Contralateral\nNone > 6 cm\n\n\nN3\nSingle or Multiple\nIpsilateral,\xa0Bilateral or Contralateral\nAny node >6 cm', 'role': 'assistant'}]