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: Unknown
[{'content': 'Wound contraction is primarily mediated by \nSelect and explain. \nA. Smooth muscle cells., B. Macrophages., C. Fibroblasts., D. Myofibroblasts.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Myofibroblasts, cells with features intermediate between fibroblasts and smooth muscle cells, appear in the wound 2 to 3 days after injury. Their active contraction decreases the size of the defect.', 'role': 'assistant'}]