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: Pathology
[{'content': 'Which of the following type of cells give rise to macrophages? \nSelect and explain. \nA. Neutrophils, B. Monocytes, C. Lymphocytes, D. Reticulo endothelial cells.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Monocytes formed in the bone marrow are precursors of tissue macrophages. After an intravascular stay of 3 days, monocytes migrate from the blood into tissues. In the tissues, monocytes undergo differentiation into macrophages.', 'role': 'assistant'}]