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': 'In a thrombus, the dark lines of zahn are due to \nSelect and explain. \nA. Coagulated fibrin, B. Aggregated proteins, C. Aggregated platelets, D. Aggregated R.B.C', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]