This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Synthesis of clotting factors needs which vitamin \nSelect and explain. \nA. A, B. K, C. D, D. E', 'role': 'user'}, {'content': "Answer: B \nExplanation: K group Catalyze g carboxylation of glutamic acid residues on various proteins concerned with blood clottingRef: Ganong's Review of Medical Physiology Twenty-Third Edition Page No:466", 'role': 'assistant'}]