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: Physiology
[{'content': 'The anticoagulant normally present in animal cell is: \nSelect and explain. \nA. Vitamin K., B. Heparin., C. Hyaluronidase., D. Dicoumarol.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Harper – 603\nHeparin is used in clinical medicine to inhibit coagulation because it binds to the specific cationic site of antithrombin III, inducing a conformational change and promoting its binding to thrombin as well as to its other substrates.', 'role': 'assistant'}]