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': 'Highest concentration of hydroxy proline is seen in- \nSelect and explain. \nA. Elastin, B. Fibrous tissue, C. Gelatin, D. Collagen', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]