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 commonest cause of massive upper GIT bleeding is: \nSelect and explain. \nA. Peptic ulcer, B. Erosive gastritis, C. Gastric carcinoma, D. Varices', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]