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': 'Primary cause of bleeding disorder in liver damage is due to \nSelect and explain. \nA. decreased level of prothrombin, B. Lack of vitamin K, C. Platelet deficiency, D. Lack of vitamin B', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]