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': 'Activity of extrinsic pathway of blood coagulation is measured by : \nSelect and explain. \nA. Bleeding time, B. Prothrombin time/INR, C. aPTT, D. Thrombin time', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]