This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anticoagulants and Coagulants, Subject name: Pharmacology
[{'content': 'Low molecular weight heparin acts on - \nSelect and explain. \nA. XIa, B. Xa, C. IXa, D. Ila', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Xa Mechanism of Action of Heparin", 'role': 'assistant'}]