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': "Most common malignant tumor of kidney in children is: \nSelect and explain. \nA. Renal cell carcinoma, B. Mesoblastic nephroma, C. Wilm's tumour, D. None of the above", 'role': 'user'}, {'content': "Answer: C \nExplanation: Wilms' tumor is the most common primary malignant tumor of the kidney in children. Ref: Schwaz's principle of surgery 9th edition, chapter 39.", 'role': 'assistant'}]