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: Pediatrics
[{'content': "A 2-year-old child with severe dehydration has sudden-onset Gross Hematuria with a unilateral flank mass. The most likely diagnosis is \nSelect and explain. \nA. Renal vein thrombosis, B. Hemolytic syndrome, C. Wilm's tumor, D. Hydronephrosis", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]