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: Dental
[{'content': 'Zone of HOHL refers to: \nSelect and explain. \nA. Cell-free zone., B. Cell rich zone., C. Pulp proper., D. None.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 1. Cell-free zone (Zone of weil)\n\nWidth approx. 40 µm\nNot always present\nAbsent in young pulp (Active secretion of primary\xa0dentine) and older pulp (tertiary\xa0dentine)\n\nCONTENTS\n\nCapillaries\nUnmyelinated nerve fibers\nCytoplasmic process of fibroblasts\n\n2. Cell Rich Zone (Zone of HOHL)\n\nMost numerous cells are fibroblasts\nFibroblasts secrete Type I and Type III collagen\nAlso contains undifferentiated mesenchymal stem cells.\nVascular supply is extensive and more than cell free zone and odontoblast zone.', 'role': 'assistant'}]