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': 'Most common malignant tumour in childhood ? \nSelect and explain. \nA. Rhabdomyosarcoma, B. Leukemia, C. Lymphangioma, D. Neuroblastoma', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Leukaemia", 'role': 'assistant'}]