This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood: RBCs, Anemia, and Polycythemia, Subject name: Physiology
[{'content': 'Longest life span among following - \nSelect and explain. \nA. RBC, B. Plalalets, C. Neutrophils, D. Macrophages', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Macrophages Life span of blood ceilsRBC: 120 daysPlatelets : 7-12 daysMonocytes (in circulation) : 1-3 daysMacrophages (in tissues) : Months-yearsNeutrophils (in circulation) : 4-8 hrsNeutrophils (in tissue) : 2-5 daysShort lived lymphocytes : 2 weeksLong lived lymphocytes : Upto 3 years", 'role': 'assistant'}]