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: Surgery
[{'content': 'How long can blood be stored with CPD - A - \nSelect and explain. \nA. 12 days, B. 21 days, C. 28 days, D. 48 days', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Blood can stored with CPD -A → up to 35 days\nBlood can stored with CPD → 21 days', 'role': 'assistant'}]