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 family of a child just diagnosed with acute lymphoblastic leukemia asks about the child's prognosis. Which of the following is a poor prognostic indicator ? \nSelect and explain. \nA. Presence of mediastinal mass, B. Age between 1 and 10 years, C. Hyperploidy with more than 50 chromosomes, D. WBC count less than 50,000/mm3 at diagnosis", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]