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: Physiology
[{'content': 'Which of the following cells become tissue macrophages \nSelect and explain. \nA. Neutrophils, B. Eosinophils, C. Monocytes, D. Lymphocytes', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Monocytes enter the blood from the bone marrow and circulate for about 72 hours. They then enter the tissues and become tissue macrophages.\nGanong 23 rd ed, pg 65', 'role': 'assistant'}]