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: Radiology
[{'content': "Abdominal Ultra-sonography in a 3 year old boy show a soild circumscribed hypoechnoic renal mass. Most likely diagnosis is- \nSelect and explain. \nA. Wilm's tumor, B. Renal cell carcinoma, C. Mesoblastic nephroma, D. Onceocytoma", 'role': 'user'}, {'content': "Answer: A \nExplanation: A i.e. Wilm's tumor", 'role': 'assistant'}]