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: Anaesthesia
[{'content': 'An, 8 year old boy, weighing 30kg is undergoing resection of wilms tumor. His hemoglobin is 12g/dL. If the threshold for transfusion is 8g/dL, the allowable blood loss is \nSelect and explain. \nA. 820ml, B. 840ml, C. 860ml, D. 880ml', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]