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: Medicine
[{'content': 'The mechanism of action of Rivaroxaban, used in the treatment of heparin induced thrombocytopenia and thrombosis syndrome is: \nSelect and explain. \nA. Direct factor Xa inhibitor, B. Activated factor VIIa, C. Vitamin K antagonist, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Rivaroxaban is the first orally active Factor Xa inhibitor. Useful in Heparin induced thrombocytopenia and thrombosis syndrome. Ref: Harrisons principles of internal medicine, 18th edition, Page 2737', 'role': 'assistant'}]