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: Surgery
[{'content': 'Minimum amount of GI bleed to cause melena is \nSelect and explain. \nA. 10 ml, B. 40 ml, C. 60 ml, D. 115 ml', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]