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: Surgery
[{'content': 'Pre-operative investigation recommended before surgical procedures in a patient on warfarin therapy is \nSelect and explain. \nA. Partial thromboplastin time, B. Clotting time, C. International Normalized Ratio, D. Differential count', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]