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': 'Lymph nodes involved in anal Ca. Is \nSelect and explain. \nA. Inguinal lymph nodes, B. Iliac lymph nodes, C. Para aortic, D. Subclavicular', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Inguinal lymph nodes are involved in anal ca.', 'role': 'assistant'}]