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: Pharmacology
[{'content': 'A useful thrombolytic agent that leads to plasmin activation is : \nSelect and explain. \nA. Vitamin K, B. Heparin, C. Streptokinase, D. Aspirin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]