This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Lifespan of neutrophils is \nSelect and explain. \nA. 6 hours, B. 1 day, C. 7 days, D. 120 days', 'role': 'user'}, {'content': "Answer: A \nExplanation: The average half-life of a neutrophil in the circulation is 6 hoursRef: Ganong's Review of Medical Physiology Twenty-Third Edition Page No: 64", 'role': 'assistant'}]