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: Radiology
[{'content': 'Thin radiolucent line which follows the outline of tooth is known as: \nSelect and explain. \nA. Lamina dura, B. Nutrient canals, C. PDL, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Because the PDL is composed primarily of collagen, it appears as\xa0a radiolucent space between the tooth root and the lamina dura.\xa0This space begins at the alveolar crest, extends around the portions\xa0of the tooth roots within the alveolus, and returns to the alveolar\xa0crest on the opposite side of the tooth.\nWhite and Pharoah, pg-134', 'role': 'assistant'}]